My CX bike develops a "death wobble" in the rear wheel when I'm going down hill at around 30 mph. So down hills are no fun on the bike, and down hills with cornering can be just slightly nerve-racking. I ride the brakes and generally avoid situations like that. On the other hand, my road bike handles like a champ. Hair-pin turns going down hill have become the thing I enjoy most of all about cycling since I got that bike. I climb hills just to be able to go down winding sections. A bike that handles well has me feeling safer and enjoying rides more.

Anyway, I've heard that narrow forks and rear triangles allow for better braking. And I've heard that less tire clearance means the frameset deals with harmonics better, avoiding the "death wobble" ... but I've also heard that isn't true.