the B board has 3.3v vdimm =)
it also gives up RAID-PATA for RAID-SATA, has mounting holes, better AGP socket placement, etc. I (and of course I am biased) believe that the NF7 and revA LP boards are equal, with the LP board of course having all the UV and goodies, and the B board (along with the Infinity NF2, which is the LanParty B board pcb/bios without all the goodies and UV) is the best there is =)