Well if you want to learn Unix you can start with
PC-BSD which is an fork to FreeBSD made with newbies in mind
Other options are OpenBSD - know for security(not to start any fights
) FreeBSD - good for general usage, NetBSD - know for very good portability.
Also there is Solaris Unix - proprietary and requires payed license if you are going to use it in production or
OI which is opensource fork of Solaris and is free of charge.
Other choice is the Unix-like Linux system with its numerous distributions. You can find hardware compatibility list here -
Hardware Compatibility Under Linux [Phoronix] Linux Hardware Reviews, Benchmarking, & Gaming Hardware for Linux - Home or on the webpage of the given distribution.
You really have to know what you want in order to choose your system
or if you prefer experimenting you can set up some system and use virtualization.
Pros of the virtualization is that you can use snapshots and revert to previous state if you mess up something, you don`t have to boot from CD and wait for actual installation every time you change the OS(there are pre-installed images for VirtualBox here -
VirtualBox Virtual Appliances | VirtualBoxImages.com as an example), you can run multiple OSes. Cons are that you cannot really do much of hardware hacking with virtualization.
There are numerous articles comparing Linux/BSD but you really have to choose for yourself. There are many things to hate and many things to love in any OS.
Here are some comparison -
FreeBSD vs Linux vs Windows 2000
And other one -
Why FreeBSD
As general advise try them in virtualized environment before you install any OS. Also don`t just go to other OS because you don`t like Windows, go in for the learning experience