If you can, wait until they upgrade their processors. They’ve been using Core2Duo’s for over 2 years. I have 4GB, and it’s pretty hard to tax the system unless you have virtual machines running. USB 3.0 is also coming out soon. Also, check 64-bit compatibility for software you will be using in Snow Leopard.
I have a 2.5 GHz MBP with 512 MB GPU, the difference in processor speed for the MB and MBP isn’t that big of a deal. However, if you are performing graphics intensive tasks, go with the MBP.