Blackberry 8320 vs 8900

Hey guys im upgrading and i needed some help, I use my blackberry mainly for messaging (eg, bbm, im, push email, sms) ive been looking at a few berrys and ive narrowed it down to the curve 8320 and the curve 8900, i enjoy the fact that both have wifi. another concern of mine is that i want to get the phone unlocked, so i want to know if all the services will still be available, i have a data plan. Obviously the curve 8900 costs more than the curve 8320 but i want to know if the 200$ price difference is worth the upgraded hardware and upgraded os considering all ill be using it for is messaging.

thanks guys