Id still say go with Skylake, new socket which means possibly more CPU's later if you need it. Whereas 1150 has hit its end.
Also new features such as more usb ports,
more PCI-e slots (which means you can use PCI-e based SSD's which will speed up CPU and read/write intensive tasks by heaps). Also DDR4, which has become cheaper compared to before.
There's no reason not to go to a new platform.
Also z170 chipsets bring features on the more expensive X99 platform onto more affordable motherboards. Heck right now I got my eyes on an Asus Ranger motherboard and an i7-6700k as well 😉
The i7 5860k will perform the best at highly threaded programs, however the other i7's not too far behind. However the X99 platforms are more expensive than...