Re: FFS
Graphics apps (the applications we are talking about here) generally don't use full floating point. Even 3d rendering software. Look at cinebench results for example.
http://cbscores.com/
No *single* xeon on that list beats the overclocked 5960x on that list. All of the higher scores are dual CPUs. (this doesn't include any v3 xeons though, however the price of those things is insane, getting me back to my original point!)
For science applications then maybe you are right. But the mac pro is not aimed at that market.
Also x99 supports 128gb RAM not 64. None of the mac pros around me have more than 64 either. I have 64GB and 90% of the renders I do don't get close to pushing that limit (even 5k architectural renders)