bcavnaugh
http://ark.intel.com/compare/82930,80807 I like the 8 Core 16 HT Cores over the 4 Core 8 HT Cores

lehpron

laser192882
I am curious about gaming performance differences between Z97 and X99. I know that they are two completely different beasts, but assuming you are using somewhat equivalent CPU's, GPU's in SLI, and RAM.

1. There are two types of gaming scenarios, GPU-bound and CPU-bound.  Usually, its the genre that tells them apart;, games that use more CPU tend to be anything multiplayer or strategy or simulation, running them at a super low resolution or getting into multiple displays.  GPU-bound games tend to anything in single-player, single-graphics card and single display all the same time.  If you get into multi-GPU setups, that makes a game CPU-bound because it has to communicate with all graphics cards; and many times getting the highest stock frequency isn't enough and we'll have to overclock just to balance the load.  It matters what types of games you play and how you tend to play to determine which hardware to get.  
2. Haswell-E (in X99) isn't different from Haswell (in Z97), it is the same architecture, same performance per clock and per core.  The "-E" is a moniker identifier originating from Intel's server platform, since LGA2011 is a server socket, X99 is just a rebranded and ported workstation platform.  There is also a Haswell-EN, -EP and -EX; but they are all branded "Xeon".

 
In games that don't use all the cores of an 8-core i7-5960X at 3GHz, the faster 4GHz i7-4790K comes off as better, for instance, from an Anandtech review on the new 8-core:

 
Another example from Techspot, page 7 shows even the infamous Bulldozer AMD nearly matches up with the Intel 8-core in GPU-bound games; while the next page 8 shows what happens in CPU-bound games.  There is a greater difference, but not as much comparing the Intel 6- and 8-cores against their quad-cores.  Evidence the games tested still don't use all the cores to show  greater difference.  So it isn't the fault of the hardware, just so far games don't need more cores-- that doesn't sopt Intel from marketing this stuff to gamers.
 
 
The purpose of X99 platform is for folks that do more than just game, it is about parallelism.  Maybe they actually want the option for 6- and 8-core processors or want a pair of true x16 PCIe slots because Socket LGA2011's have 40 lanes compared to the 16 lanes in LAG1150 (differences between x8 and x16 are marginal in gaming, but not with GPGPU computation).  X99 is about getting server-grade options at the consumer level, and some X99 boards allow for Intel's flagship 18-core Xeon-- which would suck at gaming because all cores run at 2.3GHz (it would perform in games no differently than a stock Core i7-950).
 
Conclusion:
Games are only coded/written with a certain number of CPU cores in mind, they aren't open to any number you make available; otherwise go for the $4000 Xeon and futureproof yourself-- no, that isn't how it works.  If your focus is just gaming, then get Z97-- but, so far since X58 and X79, X99 will last three year before it gets succeeded.  So far, Z-chipset get replaced faster and the upcoming Skylake architecture next summer with the flagship Z170 chipset means Z97 won't last unless you don't plan to upgrade immediately and remain a "late-adopter".
 
That being said, the 14nm shrink of Haswell known as "Broadwell" is also set to come by next spring an will work with Z97, but it will be the last.  Additionally, rumors so far don't specifically mention the existence of an unlocked Skylake coming next year at all, it would cannibalize Broadwell-K too soon.  Z97 may keep some relevancy far into 2015.  Most definitely by 2016, a Broadwell-E will come for those on X99; Intel will definitely not skip that, they offered 22nm shrink of Sandy bridge-E known as "Ivy Bridge-E" two years after X79 first debuted.