P35 is cheaper and just about as good as X38.
P35 ftw
WRONG! Thanks for playing.
The P35 chipset has fewer PCIe lanes and doesn't support PCIe 2.0 It also doesn't support Intel's XMP technology, X38 does. Again I say, X38 is the best chipset out of those listed. P35 is a great chipset and if you don't need SLI or Crossfire it is an excellent choice. However don't kid yourself for one second about it being better than X38 because it isn't. It is however just as good in some scenarios, but clearly inferior in others.