ubuntu. I generally prefer gentoo, and like where it's going, but I'm currently using ubuntu quite happily. I tried it out, and it has worked wonderfully for me, and there's no real reason to switch back.
xgl/aiglx/nvidia 3d extensions work great (just using nvidia 3d compositing), so does beryl, and the instructions to get it working are very simple to follow. It's basically, install hardware drivers, add a repository, apt-get a few programs, edit a config file or two, and restart.
I've tried SuSE a few times and have never liked it. Just my $.02