I should restarin myself from replying to this thread, but there is a LOT of inaccuracy here, and I don't want anyone to be confused.
First off, Unix is Linux, and vice-versa. That has nothing to do with graphical interfaces. A graphical interface is simply an application that you can turn on and off. Read a little history about Unix at
http://unix.about.com .
Also, there is nowhere that you can buy a product called Unix. Unix is an operating system structure. Currently, Linux, *BSD, Minix, etc... are actually "Unix-like operating systems". They act like Unix, but since Unix doesn't really exist anymore (as a product), that's as close as you're going to get.
Picking favorite Linux / BSD distributions is like picking favorite cars: everyone has their own opinions and reasons.
Linux choices include:
Redhat, Mandrake, SuSe, Slackware, Caldera, Storm, Debian, etc, etc etc...
BSD is a little more simple:
BSD/OS, BSDi, NetBSD, OpenBSD, FreeBSD...
Frankly, I think the best way to decide is to try a few out, and then decide. Check out
http://www.cheapbytes.com for some great deals.
And most importantly, learn to read all the documentation you can first! Unix helps those that help themselves. We all get questions, but most of the common ones have been answered here before. Read the FAQ, learn the Search utility, and check out the entire site before posting.
Otherwise, you'll quickly learn the meaning of RTFM...