Difference between

Nexuiz does include a linux shell scripts nexuiz-linux-glx.sh and nexuiz-linux-sdl.sh which will take the right 32 or 64 bit variant and also take care of the right directory, use those to start the game.
A few lines down in this you can also find a link for scripts that also will do a simple autorecord.

Wich is the difference between the two (glx and sdl)?

Thanks.

The SDL build is dependant upon SDL, Simple Direct Media Layer. The GLX version is not. The two options are there as one work better than the other. On some occasions one won't work at all or there'll be strange input issues or something.

In general SDL performs slightly quicker. Try both, benchmark (eg. timedemo demos/demo1 from the console) and see which works best for you. In depends upon hardware and software specs.

Both are basicly the same, just differ in the way (direct or via libSDL) they access the hardware. In an ideal world both would work just as fine.. As Ed said it depends on which system you use but if both work fine it does not matter which one you use. However i tend to use SDL as the different way it access the hardware helps with my keyboard layout..