[breakingnews]

Frame material makes a huge difference in the type of ride. It's very obvious when riding a road bike at aggressive speeds; honestly, though, I don't have a tremendous amount of experience with different mountain bike frames. Last time I rode serious terrain, I never sat down long enough to get a good feel - too bumpy to notice, anyway.

But you have the right idea. Different materials have different characteristics, and it also dictates how the frame is put together at the joints. If you ride a lot, you'll be able to tell the difference especially when cornering, powering up a hill, taking a fast descent, etc.

Trek is a good brand. Giant is also good, but some of their equipment is so-so. What you busted on your son's bike was the bottom bracket. It happens - why you should pay up a little bit to get better components.