The standout feature is that the H170 locks the cpu's 16 PCIe 3.0 lanes to the first PCIe 3.0 x16 slot. Motherboard manufacturers are not able to split these 16 lanes to other slots for Crossfire or SLI - features which Watchout cannot use anyway. With the Z series, manufacturers' priority has always been towards gamers who may want to use 2 or more graphics cards, so lanes are re-distributed when other slots are used, and it becomes a shopping nightmare if we eventually want to add a capture card or two.
Loss of other features versus the Z series, such as over-clocking, a couple or more USB 3.0 ports, 4 PCIe 3.0 lanes from the motherboard's platform controller hub (pch) are unimportant to the majority of Watchout users.
And to be frank the i7 6700 cpu is quite capable as a processor. I have been using the i7 4770 and 4790 with the Z97 boards, and it would seem I wasted some $ with that chipset as I do not use most of the extra features, and instead have to worry about losing PCIe lanes when I add a M.2 SSD. The H170 seems to be the answer to my prayers so that's the direction I'm going with my next build.