The 32bit vs. 64bit discussion is a very broad one ranging across nearly every OS. Basically, 64bit machines experience a marginal/slight performance increase in tasks that are heavily based on processing, such as video encoding. Note that video games do not fall under this category as their performance is more based around available video memory/access times.
32bit, on the other hand, offers more compatibility with apps. But in Sabayon, a 32bit emulation layer is used in the x86-64 distribution to offer the same compatibility (perhaps not by default, but it is there. Someone should correct me on this.)
I personally use 64bit edition on my tower and it works great, have yet to experience a compatibility issue.