I didn't get chance to try the N97 but the curve is a seriously sweet phone. Everything works great on it and the connectivity you get with the push email etc is great. I defo feel i made the right choice, even when comparing to iphone (i already have an ipod touch).
I heard bad things about the nokia software, although it does look like a good phone.
The support forums for blackberry are probably better too. Plus the blackberry messenger is great. I get to stay in touch with my friends in america for free!