Soldered-on RAM is another reason I wouldn't buy an Apple computer. That said, I'd use the money you save by getting the lower-end processor and upgrade the RAM to the max, as you can't upgrade it later.
Anytime I've thought I've had enough RAM I've found some situation where I was quite glad I had lots of it. You're not going to need to buy a computer for a looooong time anyway. Plus, it means you don't need to ever have a swap file.