What processor do you have? If you have a Athlon 64 or an Intel 64 bit CPU,
you'd get better performance with the 64-Bit version. The weak side to that,
is even less driver support than what is available right now, which is
limited quite a bit. It is improving every day, though.
Otherwise, use the 32 bit. You can use the 32 bit version on the 64 bit
CPU's as well.