Leather vs vinyl really comes down to personal preferences. Vinyl is much more maintenance free and no doubt less expensive. Personally, having had both, I'd opt for the vinyl. Since there are multiple layers of material between my skin and the seat (well other than those odd drunken midnight rides) I really don't get much benefit from the leather.
As to heat, I'd say get it. A heated seat is one of those things that until you experience it, you just don't know what you're missing. Don't know the science behind it, but a warm tush on a cold ride is a good thing.