Do you care what material your passengers cars are made of?

I'm good with wood/metal, Aluminum and ABS.  I have some early Walthers 60 ft kit cars that are among some of my favorites.  I mostly run them in mixed trains.  They are Pullman Green in the C&NW livery.

I don't care much for the early (pre 1970) aluminum cars as they would oxidize and get a dirty look.  Some like that, I don't.  Early 80's painted aluminum cars would chip to easily and detract from the appearance.  I think manufacturers have finally got the painting process right.  With that said, my favorite painted aluminum cars were produced by K-Line offered through the K-Line collectors club in the Golden State livery.  Good detail and looks.  I pull them with a Williams Rock Island E7 AA's converted to TMCC with ERR Cruise Commander.

With regard to the ABS cars, I like them all, heavyweights and streamlined both.  Some of my favorite are the MTH Blue Comet heavyweight set and the Texas Special streamlined set being pulled by the Lionel PWC Texas Special ABBA lash up. 

There's alot of good answers. I looks like the highly detailed scale plastic cars have the lead.

FWIW

I like prewar tinplate followed by early postwar tinplate O-Gauge .

Lew, you got that right!

Nope.

I strongly prefer aluminum for streamlined cars, including painted ones, but I don't rule out plastic for a painted set if it is well done. I have a set of MTH Kansas City Southern cars that I am quite happy with. The rest of my passenger streamliners are all K-Line aluminum. I don't have any polished metal cars because I don't collect Santa Fe, Burlington, etc. but if I did I would certainly want those in real metal, not painted plastic. 

Sometimes you don't have much choice: if you want a certain road name or variation. I really haven't seen any 'Madison' style cars made in aluminum. So it really matters what you are looking for; I don't think many of us would turn down something made in a material that we would not prefer if it's what we like. I like both for that reason, but aluminum is much nicer compared to the same style made in ABS.

I'm with Matt on this one. Give me quality, or give me death...wait a minute, wrong speech. Anyway, give me quality first.

I run aluminum and plastic. The plastic are great for running longer trains on grade due to weight, but the aluminum sure do look like the real thing. Either way I'm having fun and that's what counts most.

The majority of mine are plastic. I have four 21" aluminum Weaver N&W cars that are very nice. My first criteria is length. 

Gilly