The hi-res screen just allows you to fit more tracks on the screen.
Speaking for experience, when I went from using my 13" (1280 x 800) Macbook to using a 15" MBP (1440 x 900) for my audio work, I was extremely happy with the extra space. I'll be ordering the high-res screen for my Macbook Pro upgrade in a few weeks time.
If you can afford it, I'd say go for it.
J