Linux is the (best!!) OS, everything else surrounding the core OS is what comprises a distribution (RedHat, Mandrake, Lindows, Suse, etc).
Each distro has its good and bad, weak and strong. It really comes down to very specific requirements on your part and opinion as to which distro is "best".
I like Mandrake -- it worked for me whne RedHat wouldn't and (at the time) Slack couldn't. Don't get me wrong, I've used many distros, including some of my degree with Slackware, and some usage of RedHat.
There are plenty of supporters for each major and mainy of the "minor" distros. The neat thing is you can try almost all of them for next to nothing. Go to a place like
http://www.edmunds-enterprises.com/ to get any number of different distros for next to nothing.
On another personla note, I would stay away from Lindows, but purely for philosophical reasons -- I don't like their approach to the Linux world at large. In my opinion they've hung their hat n the M$ hat rack and would rather be there than swimming with rest of the Linux distro makers and users.