This is the subject of endless debate. I did a lot of reading and research, and determined that I would be using track power (actually DCC).

From the type of operation I wanted, batteries were too expensive in every loco, too many chargers required, and small locos could not have adequate power. I also read a lot about people cleaning track, and tricks to keep electrical conductivity. This all did not fit the way I wanted to run trains, thus my personal choice.

Note: 6 years later, my observations still hold, and I'm very happy with my choices.

To start off, the biggest choice is the type of rail you will use. You will also want to determine the tie spacing (standard gauge or narrow gauge).

I've compiled a table of the different types of metal rail that track can be made from. Of course, if you are running battery power, your track could be made of wood too, but but we'll concentrate on metal here!

Notice I am only talking about the rails. The ties are another concern. At this time, most plastic ties are fine for about 10 years in the sun. Wooden ties WILL require maintenance, such as stain or preservative. Don't use wood that termites like!

Aluminum Rail:

My conclusion is that aluminum rail is great for battery powered layouts, where you never (electrically) clean the track, or where cost is a major factor, or you are in a really dry environment where corrosion is minimal. It is not good where you have large critters visiting your railroad and standing on the track, like deer.

Brass Rail:

My conclusion is that brass is a good choice for many people, having a good balance of cost and performance, and works well with track powered systems. There are many ways to keep the track electrically clean, and MOST people will spend significant time cleaning track.

Nickel Silver Rail:

My conclusion is that Nickel Silver is not "better enough" to justify the cost over brass if what you want is less cleaning of rails or better conductivity. It just has not proven itself superior outdoors to brass.

If the more prototypical color of weathered rail plus the slightly lower maintenance is worth it, than NS might be for you.

Steel Rail:

(I'm only including this because newcomers always ask about it.)

Note: The Bachmann hollow steel rail can rust through in one season, don't do it!

I can't really see a reason to use steel rail outdoors. Maybe if you used long sections of solid rail in flex track, used welded steel electrical jumpers, dumped oil on the rails on a regular basis, and cleaned it every day it would be ok outside.

Stainless Steel Rail:

More costly than brass, shiny rail. Lack of many different codes (sizes). Excellent in wet, corrosive, dirty environments. No maintenance to speak of, very tough and durable.

My personal pick, but my my highest (personal) priority is to have fun, and have reliable operation. No problem with corrosion, and I don't mind the shiny rail. Very good choice for track power if you use slightly more feeders, overkill for battery power.

Manufacturers by material and code (size)

Comments on some rail manufacturers:

H&R Stainless

The H&R stuff is wonderful quality, the tie plates look a little european. The SS grade is 430 > 434.Grade 430 is a ferritic, straight chromium, non-hardenable grade, combining good corrosion resistance and formability characteristics with useful mechanical properties. Its ability to resist nitric acid attack permits its use in specific chemical applications but automotive trim and appliance components represents its largest fields of application.

It has slightly lower corrosion resistance than 304, and stiffer / less ductile. This alloy is typically cheaper than grade 304.

Grade 430F is the free-machining version of this grade, available in bar form for use in automatic screw machines. Grade 434 is the molybdenum bearing version of Grade 430 and has the same useful combination of properties. Its molybdenum addition improves corrosion resistance.

The joiners are a slip fit and have great conductivity, there is a patented wedge on the bottom that makes great electrical contact. The plastic of the ties is on par with LGB for durability, they are brown. They have only one switch though, an 8' diameter, that is a severe limitation.

Originally, it was made by TdV, Trefileries des Vosges, Le Blanc Murger. TdV started manufacturing this stainless steel track in 1990 as a special product line to supply the needs of a new large French amusement park with a model railroad.
Revalda in Switzerland took over the marketing and sales of that track system in 1991 and on January 1, 2000, Revalda started their own manufacturing of the track system. TdV at that time reverted back to their core product line.
http://www.revalda.ch/revaldagleissystem.html

(The following prices are from the web site, July 2007)

They have the following curved track (diameter in feet) 4,5,8,9,10,11.5,12.5,14,15,16.5 - A 10 foot diameter circle would cost 16 times $18.76 (a section) or $300.16.

They have 12", 24" straight, and flex track.

One wild thing: you can have either their joiners or Split Jaw clamps when you order flex, no price difference!

The 8' diameter switch is $158

The stuff is sold only from H&R, and at list as far as I can tell.

12" straight $9.20

24" straight $16.97 ($8.49 a foot)

Flex comes in various lengths, best price is 120"/10' package, $74.48 ( $7.45 a foot)

AristoCraft Track in General:

Made in China. The supplied rail joiners have screws on only one side to affix to the rail. The screws are very small 2mm diameter hex head cap screws. The joiners themselves do not conform closely to the rail (especially the stainless ones) and since the screws are on only one side, do not do a perfect job of aligning the rails. If you use their joiners (and I do not recommend them for track power), you would do well to change the joiners to clamps. Aristo-Craft makes very inexpensive clamps that are ok..

(explanation): Since the joiner usually does not fit snugly, often power is transmitted from the rail to the screw head which then contacts the joiner, then through the joiner to the other screw head and back to the rail. The contact area under the head is small and it makes poor contact, and the screws loosen. To make matters worse, one of the holes in the joiner is a horizontal slot, which makes even less contact. Another small irritation is that a small percentage of the rail sections have the screw holes drilled too far up or down in the rail web, which makes it almost impossible to use a joiner, or you enlarge the screw hole in the joiner so much that electrical contact goes out the window. In these cases, get a rail clamp and save yourself some grief. Virtually no one has been successful drilling and tapping new holes in the stainless rails, and it's touch in the brass, even though you can buy a drill and tap kit from Aristo.

The ties are black, and the "tabs" that hold the rails to the ties are small, fragile, and have a fair amount of slop. It is easy to pull a tie off the rail with normal handling. The tie material is UV protected (there was a batch long ago that was not), but it does weather faster than most other brands, though about on par with USATH. The ties are very uniform, so not a real prototype appearance.

The switches likewise have some problems. The number 6 switch suffers from electrical reliability and sloppy flanges and rail alignment and a too deep flangeway at the frog. See the Train-Li insert for the frog. The microswitch often jams, and causes short circuits. See the specific sections on Aristo track.

The wide radius switch (10' diameter) needs about 1/2 hour of tweaks to make it reliable, although in 2009, Aristo finally improved the frog to eliminate half of the problems, see the specific sections on Aristo track for tips.

Also, as of July 2007, there is no UV stabilizer in the throwbar and either switch, and many people have them disintegrate. You can get replacements from Aristo. Be sure to request the brass bushings also, since they typically seize in the throwbar.

Aristo has a wide offering of sizes, from tight to very broad curves, 3 different turnouts, 3 different crossings, just a great selection.

(The following pricing is as of July 2007, after the 100% price increase)

Straights come in 12", 24", 36", 54", 60", the 12" straights retail for $10.33 each (from a box of 12), and 60" are $52 or $10.40 a foot (from a box of 12).

Curves come in (diameters by the foot) 5,6.5,8,9,10,11.5,12.5,14,15,16.5,20 a great selection. A 10' diameter circle would cost 12 * $25.33 or $304

The Wide Radius (10' curve) switch is $140, and the #6 is $364 !!!, there is also a #6 Wye at $250 (this does not make sense!)

Flex track is available, the best price is if you buy a bundle of rails (24 x 8') for $820 (96 lineal feet of track) and 2 packs of 48 one foot tie strips (96 lineal feet) for $122, so 96 feet costs $942 or $9.81 a foot. I did not check if joiners are included, but getting split jaws would add about $2 per every rail, so 24 rails = 48 dollars, or 50 cents per foot, so if you want to compare with H&R's offering, the flex track is about $10.31 a foot all told.

Please note that Aristo track is often discounted, so if you are comparing prices, get the "street" price from your favorite supplier.

Big note: the sizes advertised are NOT the actual lengths, the 5' track is one inch shorter, and likewise all straight sections are not as advertised. Also, the curve diameters are not as advertised. I will look for the "real" dimensions, but the track is made to metric sizes. Many people have designed layouts based on the advertised dimensions. Aristo is unique in this area, all other manufacturers give real dimensions.

From Jerry McCoolgan on the MLS forum:

For what it is worth my 1995 Aristo-Craft catalog lists:

ART 11000 12IN./ 309 mm. STRAIGHT TRACK

ART 11060 24IN./ 610mm. STRAIGHT TRACK

ART 11070 36IN./ 914mm. STRAIGHT TRACK

ART 11090 60IN./ 1524mm. STRAIGHT TRACK

 

plus a 12 IN. CURVE TRACK and one each left and right switches.

 

By comparison there were 29 FA-1s and 25 FB-1s to choose from.

 

In 1996 the track had more than doubled and the above were shown as:

ART 11000 1 FT.30CM

ART 11060 2 FT.60CM

ART 11070 3 FT.90CM

ART 11090 5 FT.150CM

 

Obviously it could not have been both 1 foot and 30 centimeters so the dealer could have explained that it was 300 mm which would be close to 1 foot.

 

Also in 1996 more curves were added and listed as MED 5'; LG 8'; X-WIDE 10' and XX-WIDE 20'

 

By 1998 the metric numbers were dropped and eventually the MED; X-WIDE; and XX-WIDE were dropped.

Aristo stainless track is 304 or 18-8 ( from 18% Chromium, 8% Nickel). Type 304 (18-8) is austenitic steel, possessing a minimum of 18% chromium and 8% nickel, combined with a maximum of 0.08% carbon. It is nonmagnetic steel, which cannot be hardened by heat treatment, but instead must be cold worked to obtain higher tensile strengths.  The 18% minimum chromium content provides corrosion and oxidation resistance. The alloy's metallurgical characteristics are established primarily by the nickel content (8% mm.), which also extends resistance to corrosion caused by reducing chemicals. Carbon, a necessity of mixed benefit, is held at a level (0.08% max.) that is satisfactory for most service applications. This alloy resists most oxidizing acids and can withstand all ordinary rusting.

Sunset Valley RR stainless.

A newcomer to SS code 250 rail, they started with flex track. The ties are brown with a web (hidden by ballase) down the center. Nice detail on the spikes and tie plates. This is the same tie strip used for their other track, so expect no problems.

At the 2008 BTS they sold 30 foot (unassembled) for $170 or is $30.95 or about $5.66 a foot. about 50 cents a foot higher than July 2007. They have a #6 at $118. So far, preliminary reports are good. With the increase in Aristo SS track, SVRR is suddenly competitive. They say the stainless is 18-10.

I have no idea what the ss grade is.

They make SS switches now, and have #6, #8 and #10 as well as wyes. This stuff looks really good.

Comments on some brass rail manufacturers:

AristoCraft

In 2008 there were a lot of changes. After trumpeting how high the copper content of their brass rail is, and how other manufacturers have less copper, Aristo brought out a low cost brass line with less copper in it. Hmmm.

USA Trains

Piko

Sunset Valley

LLAgas creek

LGB

AML

Comments on some aluminum rail manufacturers:

AristoCraft
is supposedly going to manufacture this, announced in 2008, not available yet in early 2009

Manufacturer reference

Llagas Creek Railways - code 215 and 250
Sunset Valley Railroad - code 250 weathered brass, aluminum, weathered nickel silver, stainless steel, switches (brass and NS), rail clamps
H&R Trains - code 332 Stainless Steel track, with either US or European sleepers

Rail clamps / joiners:

How you connect your rails depends a lot on whether you run track power or not.

If you are totally battery and will NEVER try track power, do anything that works. Be careful about expansion and contraction.

If you need track power, you need a good way to ensure power flows and you are not chasing loose rail joiners. 

See the section on "Track Power / Wiring" for more details.