IIRC, I remember benchmarks from a short while back (too lazy to google for them) and the performance, when OCed to the same clock speeds, between the 2500k and 4700k was within the margin of error. There’s been like no improvement to CPU architecture, for gaming*, until semi-recently.
With AC:O, maxed, I average 55-ish fps in the benchmark regardless of 1080p or 1440p. Probably the first game that concerned me with my CPU since switching to the i7.