Why not a Bold 9900?
Iphone will be better for apps and web browsing. In my experience, it sucks as a phone though, and it feels quality but the hardware and firmware is not that reliable. The BB is better for calling/messaging, but it's losing app support (google decided to not support BBOS7 with google apps) and the apps it does have don't have that "slick" feel to them.
I currently have a Bold 9700 and it's been a great phone, but it's time to replace it. I'm currently stuck between the 9900 and S2 Skyrocket, and will most likely end up with the droid.
It basically comes down to what you use your phone for most. Calling/messaging? I vote BB. But if you use apps a lot and are always browsing and playing games, without much talk/text the Iphone will suit your use better.