centos is for servers,
no point in trying mint as its basically ubuntu,
in my opinion there is no 'good' distro of linux, they all do the same job with the same software,
its the way they look thats different
linux is the heart of the operating system, all the rest is added bits by companies,
for instance, i use mandriva linux, it has the kde4 desktop and i use k3b for burning cd's,
all versions of linux that use kde also use k3b for burning cd's,
i use dolphin - so does every other kde version
i use kwrite - so does every other kde version
i use kmail - so does every other kde version
do you understand what i mean ?
its the same with gnome versions, they all use nautilus, braserio, etc
one of the main differences in the kde versions is the name,
eg mandriva, pclinuxos, kubuntu, etc
other differences in all versions are the packet/software manager,
i use rpm's with drakrpm, some others use deb's with synaptic, some use rpm's with synaptic, some use rpm's with yast, etc
but they all contain the same software
linux and the various distro's also have specific commands,
in all versions of linux these commands will work
http://ss64.com/bash/
but distro specific commands are designed for one distro,
for instance - installing software
sudo apt-get install someprogram
will not work on my system,
i do not have sudo and i do not have apt
the command on mine would be
su (add password)
urpmi someprogram
what i suggest is pick a distro you like the name of then learn how to use that one, sounds odd but its they way i chose one and i've been using it now for over 5 years,
here is a list of desktop live cd distros to look through
http://www.livecdlist.com/purpose/desktop
source - mandriva linux user (the best distro)