Memory is a big difference with 2d-3d graphics But for using more memory you need to have 64 bits
And ,during the last 3 years, lots of  programs are going to have 64 bits version (Vue d'esprit, photoshop, carrara pro ,etc) And utilities are too going to have 64 bits versions (ex:O & O software like diskimage,defragmenter etc)
Windows 7 64 bits is excellent  Go for it
I have lots of softs (32 and 64 bits ) and everything working on my 64 bits system and 8 gigs ram