well CentOS / RHEL / ScientificLinux is not the best choice for a desktop install
it can be used , the current is RHEL 6.4
but i DO NOT use my ScientificLinux 6.4 install for everyday use ( except on a 12 year old computer that needs legacy support)
it is not the best tool for that .
i run OpenSUSE 12.3 as my everyday OS
I was running Fedora for many years BUT fedora has it's own set of issues
-- it is a good OS... BUT ....
and it is a big one
It is a VERY fast passed Research and development distro
one that has a NEW release EVERY 6 months
and it is recommended to do a new install every 6 months with each new version
-- this is a lot of work on your part --
OpenSUSE 12.3 is nice , a bit bloated , it is targeted more for office use and home use
And has a longer lifespan that fedora. SUSE supports 2 versions and for 18 months
Ubuntu ????? mixed feelings on that. Do a bit of research and make up your own mind on it's privacy polices
I will not use it , but others like it .
Mint Linux , it is a member of the Debian family and a LOT of people like it
( the red hat and Debian families )
CentOS and fedora and SL are part of the red hat group
Mint and Ubuntu are part of the Debian group
Debian , very stable but also not the best for a home desktop
For the office - good ,for running a server VERY GOOD .
and OpenSUSE ( novell)is well ? sort of in the red hat group
it uses the rpm packages but that is about it
Novell is a business competitor of Redhat
SELS11sp3 VS. RHEL 6.4
try a few , then you can decide for your self what you like
Both OpenSUSE 12 and MintLinux 14 are good for "new to linux" users