I'm not really sure what ATB/XC All terrain bike? dunno. I will be commuting on a hilly campus (main) but I want to get into the sport, so... offroad...no huge jumps, just stuff under about 4 foot (maximum). But i guess this is important so i'll mention it. I ride very hard. And I mean very hard. I like taking the hard route. The harder the landing, the more i'm gonna like it.... as a rule of thumbs. That sort of thing. Don't know if that helps. According to the guy at the bike shop, the rockhopper has a lighter frame and better shocks. he said that is where the $100 difference is. The front suspension has some kind of dampeners in it or something. Not really familiar with this stuff yet. So I'm sorry about the extreme ignorance. lol