I've always preferred Facebook.
I did join MySpace years ago, but never really did much on it.
A couple things that really annoy me about MySpace is the fact that people overdo the layouts in their profile and the way they leave comments on your wall.
Some people have 5 different flash animations, a video player, a music player, a bunch of animated GIFs, horribly colored text and images, or whatever they have that gives anyone a headache. I've seen some people use black text on purple backgrounds or purple text on black backgrounds. I've seen some use animated images as background images and it makes the text harder to read.
As for leaving comments, whatever happened to a simple "Hey, how are you doing? How was Spring Break? How was Christmas?" "Ready for the summer?" Instead, I get one over-sized animated image with a simple over-sized sparkling word that says... "HI!" "HELLO!" "GOOD MORNING!" or whatever.
With Facebook, it's all simple and I can control what I want and don't want to see.