There are 2 different types of bikes that I know of, sit down (the ones with the back on them) and the sit up ones. Is one any better for you than the other?

I think neither one is better than the other, it's just what YOU are more comfortable with...

Sounds good to me. I don't know if it's the way I'm sitting or what but if I'm on a "sit up" bike, I can do a good 2 miles more than I can on the "sit down" bike in the same amount of time.