Well I dont have any personal experience of either yet, but ill quote the conclusion from cpc for you.
"Given that the Intel 975X chipset is the company's top-of-the-range offering, you'd expect boards based around it to run faster and overclock further than those using the more mainstream P965 chipset; in our Core 2 Duo tests, however, we've found the opposite to be true. This means that the only advantage the 975X chipset has to offer is CrossFire support. While the PW5 DH Deluxe can overclock to the same frequency as that of the P5B Deluxe, it just isn't as fast, so unless you're dead set on CrossFire, the slightly cheaper P5B Deluxe is a much better buy".