Blackberry 9700 vs Blackberry 8820

I currently have a Blackberry 8820 with ATT. I have an unlimited data plan, however it is not the Blackberry data plan (I dont have BBM....the unlimited data plan is something that ATT offered a long time ago and I have been grandfathered in for years).

My questions is this: I am looking to get the Blackberry 9700, without a contract so I do not have to pay the high price Blackberry data plan for 2 years. Will the internet speed on the 9700 be significantly different on the 9700?

Also, does it matter if I were to purchase a T-mobile 9700, unlock it, and use it on the ATT data network?

Thanks!

Yes. The 9700 has 3G capabilities, while the 8820 does not. And yes, it will matter. The T-Mobile version of the 9700 uses different 3G bands than the one on the AT&T version, thus you will not get 3G if you were to use the T-Mobile branded one.