I ran across an interesting forum posting about the differences of 32 vs 64 bit python.
Check it out here: http://forums.arcgis.com/threads/70241-10.1-sp-1-and-32-64-bit-Python-versions
It's worth a good read to understand if you install the 64-bit background processor provided at SP 1 how it operates and works on your machine.
Remember if you do install the 64-bit version of python, you will have to install the 64-bit of all your extensions as well.
Enjoy