I was in the same dilemma and got the 2.2 GHz with 128 of video RAM. From what I read the 256 only offered a bit more performance. My main use will be as a pro photographer using Lightroom, Photoshop and sometimes Aperture. If i was to play newer games or use Aperture extensively then the extra VRAM could be useful. However i am not a gamer and with 128Mb VRAM i have been told that Aperture is acceptable.http://www.barefeats.com/rosa03.html
All that said I got the 2.3 128 base model as to upgrade the hard drive to the faster 7200rpm would mean a delivery of nearly two weeks and i needed it now. I will upgrade the hard drive at a later stage. As for memory i will upgrade to 4Gb but not from rip off Apple but from reliable vendors like Crucial (in the USA) for about $280.