Choosing CPU for workstation

So I wanted to upgrade my computer. My current computer: CPU i5-3570k (4c, 3.4GHz) GTX 1070.

And I am choosing between i7-6700k(4c,4GHz) and e5-2620 v4(8c, 2.1GHz).
I am wondering if 8 cores will make it run faster or I should choose a 4 core cpu with higher clock speed.

Very basically, more cores = faster lighting builds, faster compile times. Faster cores = faster in game/editor performance.

I don’t think for value you can compete with the i7-5820k still. 6 cores, 12 threads, runs at 4-4.2GHz with a one-click overclock on stock cooler. Good balance of cores and single thread performance…I don’t think there’s a better value CPU for UE work out there.

Isn’t the i7-6800K the replacement for the 5820k? Either way, that is probably the best bang for your buck, and the best middle ground. I’m using an overclocked 5930k (just because I got it for cheap), it’s basically a 5820k, it’s a great processor for UE4.

depends on what you rly want, amd or nvidia look at