The P5B has 2 PCIe 16x slots, but the chipset doesn't support SLI or Xfire (maybe with some 3rd-party tweak later on). The P5B Deluxe/Wifi comes a wireless adapter, if you need one. Finally, the P5B uses a heatpipe system to cool the northbridge. Other than that, they're very similar boards. Both motherboards are excellent overclockers, and of course are high-quality.
I see no real advantage of the P5B over the DS3. Come to think of it, I should've ordered a DS3 and saved some bucks
. Well the P5B is black and does look cooler, but it's not worth the extra $30.