Your best bet is to try a few different live CD's and see which one you like best.

A discussion like this is never gonna have just one good answer - it's rather like asking "what car should I buy". Everyone will have different opinions for different reasons.

FWIW, I'm a big Ubuntu fan and have been a UNIX SysAdmin for far too many years using SCO Linux, HP-UX, Solaris, Redhat, SuSE, BSD, etc etc etc.