Comment by themafia

XOR and SUB have had identical cycle counts and latencies since the 8088. That's because you can "look ahead" when doing carries in binary. It's just a matter of how much floorspace on the chip you want to use.

https://en.wikipedia.org/wiki/Carry-lookahead_adder

The only minor difference between the two on x86, really, is SUB sets OF and CF according to the result while XOR always clears them.