depends on how comfortable w/ linux you are. If your new to it try 3.x first, but if your comfortable with playing around on the system then give 4.x a try
I'm very good with x86 Linux I'm a PPC Linux noob and reasonably familar with OS X. I did load 3 for now and it works nice I will try 4 when I have some more time to tinker.
being confortable w/ x86 linux you'll do fine - only thing you'll have to take a look at is compiling a new kernel. Less options then x86 but far diff hardware