I’m going to go with the 15″ with 2GB ram
1) going to buy cheaper RAM later. Apple is really expensive
2) we have a 17″, and sometimes it’s just a little too big. Plus cramming that many pixels onto that size screen doesn’t really give you much more real estate… because everything will be SO small. Rather plug in my Cinema display
3) if I were you, I’d never use the internal for media. Unless it’s an emergency. Laptop HD’s are notoriously prone to failure when they get beat on.