I've played Nexuiz off and on since I started using Linux as I heard it was the game with the best graphics. However, I started playing Sauerbraten just today, and WOW it looks great. I don't know if it's just that I like the level design better or what, but I think it is a truly fun game and looks great.
If I had to choose between the two I think I prefer Sauerbraten so far. What do you guys think?