64bit can support more processors with more cores than 32bit as well as the extra memory. Also from what I've seen myself in the last week or so the 64bit version of 7 is more stable than the 32bit version.

The only setting I changed for Poser was to have it always run with Administrator access, it's even installed to the Program Files folder, I know I probably shouldn't but I wanted to prove to myself that it can be done.

Windows 7 64Bit
Poser Pro 2010 SR1