Really depends on if you want to have the convenience of taking it with you to school.
There are laptops that are just as good as desktops, but they cost considerably more than the equivalent desktop.
For photo/video editing and such, I recently used my Inspiron 9300 laptop (1.6ghz, 1.2gig ram) for editing a 2hr video/dvd project. It worked pretty good, using apps like Adobe Premier, Audition, Encore DVD, and Photoshop. I was a bit rushed with it, and still have a few things I want to tweak on it. Never got around to using After Effects for some stuff, will be doing that when I get around to finishing it finally.
Got this laptop in March last year, was just under $2000 (mainly due to the 17" wuxga screen). You could get the same system for around $1500 or less now, I'd think... especially if you're willing to go with a smaller screen/not quite top of the line.
Graphic Design / Photography / Web Design