B... and you won't need to worry about 64-bit drivers for any OS. (See post above)
I would not know how it is on the Windows side but in Linux 64 bit clearly wallops 32 bit. (http://www.phoronix.com/scan.php?page=article&item=ubuntu_1204_3264&num=1). The way I read the lengthy discussion on the forum, It is a no brainer to select 64 bit if you have a GB of DRAM in a headless box or 2GB with a GUI. 64 bit is a big deal that does affect performance even for for memory constrained environments.
