All about the Ram
You won't really notice the difference in processor IMO.
I went with 16GB Ram and luckily I did. My usage is very similar to yours (Aperture, PS, AI, FW, RCT III, Lots of Tabs open) - not all at the same time obviously but using 1-4 of those at a time; and would be paging out a lot if I didn't have the extra.