I want to buy it

Harder to answer than you might think. When you're talking about Windows, it's easy to say what the newest version is because one company is creating one product.

Unix refers to a whole handful of different flavors.. here's links to a few:

AIX
FreeBSD
IRIX
Linux
NetBSD
OpenBSD
Tru64
Sun Solaris
SCO (openserver and unixware)

http://www.unix.com/where-do-i-download-linux-unix/

where is unix?
Diffrent versions of Unix/Linux

So as you can see the newest version depends on what flavor you want to use.. and really the only way to pick is either at random and learn one or decide what you need the flavor to do and do some research. And don't even bother asking which one is the best - they're all different.

I think I see a pattern here...Lanstarr. You are obviously new to UNIX and that is great keep posting and reading and learning.

However, please try to ask specific questions instead of rather broad and questions that engender "chat room " style responses based on opinion...

This site is dedicated is to provide answers to specific questions and be a repository of information for UNIX users to access.

I am not flaming you, but just tryin to guide you in the right direction...

I am going to close this post, but please continue to post and ask questions, just specific ones. Thanks.