If your room is really well sealed and climate controlled, it shouldn't make a difference, but mine's not, so it does to me...
Soilless is just that...anything but soil. I've never seen anyone use straight peat, i think in most cases that'd be a bummer. Sunshine Mix, por exemple, is peat BASED, but has all sorts of other stuff in it: perlite, vermiculite, some kinda compost probly, etc. The mix I'm using right now contains: coco fiber, forest humus, perlite, lava rock, earthworm castings, fish bone meal, feather meal, bat guano, seabird guano, kelp meal...the list goes on. I like that it's called "Basement Mix," 'cause that's where we used to mix up a similar mix in kiddie pools.
The best herb I can remember smoking was grown in a soil/coco mix, with some other stuff: perlite, vermiculite, worm castings, mushroom compost. I think you have the right idea there, brainiac. Anything soil just wigs me out a little, 'cause I'm so used to soilless I'm likely to overwater.