I have a Trek 870 Mountain Track with a stock saddle that is uncomfortable on longer distance rides. Looking at WTB Pure V saddle but wanted to know the difference between the Comp version and Race version since the later is about $20 more.

Race = 320g and Cromoly rails.
Comp = 360g and Steel rails.

I am not too worried about the weight. Do the steel rails affect comfort that much compared to the other?

I recently bought the pure v race se from Performance and it's still on sale:

WTB Pure V Race SE Saddle - Men's Bike Saddles

Great saddle.

I found that one uncomfortable for rides more than 5-6 miles. I replaced it with a brooks, which was immediately better for me, shape wise. Even new, I haven't had any discomfort issues at all on a 15 mile ride. I don't even have 50 miles on it, and I'm already a proud member of the Brooks Brigade(tm).

Probably not fair to compare the two because of the price difference though.