Rumjungle's got good core advice here. We have a MacBook (13" white) and a MacBook Pro (17") in the house, and the build quality between the two is very, very different. If you can, handle one in a store or from a friend. The keyboards are definitely worlds apart, too.
RAM sadly taps out at, I think, 3GB for even the MacBook Pro's - get as much as you can. For Photoshop and video editing scratch disk usage (both very intense), 7200rpm hard drives can also make a big difference. So, depending on your budget, you could look at a souped up 13" MB or more standard 15" MBP.
Oh, and don't forget about the screen you'll be editing on. This is where there is a big difference between the MB and MPB line. If you have an external monitor for editing, this may be less of an issue. The resolutions between the two screens may also be a significant factor.
Either way, for what you want to do, either is an adequate tool and you're likely to be totally thrilled either way. I'm a freelance imaging and design professional so the build quality and firepower of the MBP line appeals to me, but you may be different and should take that into account.