Anyway, I haven't played with any Blackberry since a little bit after Pearl so probably I can't say much. Choose the one you like best. I personally saved myself from two generations of iPhone and bought 3GS on the 2nd day it launched. Now I can't live without it. :)
Update: Web browser on the Curve is much better than the Pearl. But still the screen is still small, needs the ball for navigation. Although it's compatible with Flash, iPhone browser is still much much more usable.