for a while I have wanted to upgrade my PC so I decided to do it in stages so that I could enjoy the benefits of each bit I as i got them. My system was;

Athlon phenom II 640
8GB ram
some asus mobo I cant remember
2x 1TB seagate 7200 sata
coolermaster case (unsure which one)
MSI 560Ti gfx

So far I have upgraded to

Corsair 330r titanium case (ATX)
EVGA supernova 750W full modular PSU
Samsung 850 PRO 256GB SSD
2TB Seagate 7200 Sata
ASUS Strix GTX 970
Logitech k800 wifi keyboard
Logitech g502 mouse
Logitech G930 wifi headset
Razor Goliathus mousepad

so now all I have to do is CPU/MOBO/RAM and Id rather move back to intel, however due to their never ending upgrades and tick/tock ranges I am stuck with a choice that has disadvantages and advantages in different areas.
I'm mainly looking at; (using computerlounge as price example)

ASUS Z97-A/USB3.1 Intel Z97 ATX LGA1150 USB 3.1 Motherboard
Intel Devil's Canyon Core i7 4790K 4.0GHz 8MB LGA1150
Corsair CMD16GX3M2A1866C9 Dominator Platinum 16GB (2x8GB) DDR3-1866 CL9
Total: $1162.15

or

ASUS X99-Pro/USB 3.1 Intel X99, DDR4, ATX, LGA2011 Motherboard
Intel Haswell-E Core i7 5820K 6 Core 12 Threads 3.3Ghz 15M Cache LGA2011
Corsair CMK16GX4M4A2400C14 Vengeance LPX 16GB (4x4GB) DDR4-2400 CL14
Total: $1526.60

either would be cooled by a corsair H80i (which I would get at the same time)

For gaming, the 4970K wins...and I do like to play a fair bit of games (but im not that hardcore into it anymore)
For multitask, the 5820K wins....I do a fair bit of virtualization and a moderate amount of video rendering from time to time

considering future proofing (which isnt ever really possible) I wouldnt have to upgrade from DDR4 but I could go faster, the DDR3 is the absolute max that mobo can take, however on the other hand the chance of a good broadwell CPU coming out for Z97 is perhaps more likely than for X99.
Both have USB C and onboard ac wifi (not that I would use that) 
With the x99 I see a greater chance of only having to upgrade the CPU.
Im not one for overclocking much.

After typing all this I realize now that I just flat out cant decide if x99 is worth the price difference. first world problems.