I think the Hardrock is a better value than the Rockhopper. The advantage of the Rockhopper these days is that it has a lighter, equally strong frame & slightly better components. But the Rockhopper starts at around $600 if I'm not mistaken. For $550, you have get a Hardrock Sport Disc with Avid BB5 brakes, double-wall rims, & a fork with lockout (nice for riding on paved roads). My LBS recommended the Hardrock Sport Disc over the Rockhopper unless I planned on at least going with the Rockhopper Comp Disc, which is $220 more. If you have the money or can find a good deal on a newer used Rockhopper (within 2 or 3 years old), I would definitely go with that. There's no denying that it's a better bike. But since your initial budget was $300, I think the Hardrock would be a better value since a Rockhopper worth the money would cost over double what you have now. The Hardrock Disc is also a very good bike, but it has cheaper brakes, no lockout on the fork, & regular rims (double walls are much stronger & will cost less in time when you don't have to get them trued after taking a 4 ft drop).