R2 vs R3 x51 pros and cons?

Hey all, new to the group. I have enjoyed my Alpha R1 for many years and swapped the i3 for a i7 4785t and added an ssd. It still boots instantly and holds it's own on many games at high settings but as i have moved onto sim games I have decided to switch it for an x51 for a better gpu. Ignoring the stock cpu and gpu is the newer r3 with the 1151 socket and faster ram worth the extra. Which ever I choose will get a 1060 6GB, 1TB ssd ( I doubt I would ever get a m.2 ssd) and a suitable i7.

R2 would be 4790k
R3 would be 6700.

So what are the pros of the r3?