The important thing to realize is that CPUs can go into and out of idle states very quickly, well under a millisecond. Assuming the game is GPU-limited or you're using vSync, there is a fixed amount of work to do per unit time and the CPU will idle the rest of the time.
OK, I'll give you that if the game is GPU limited, the amount of energy used could remain equal. If the bottleneck was at the CPU, however, the S model would still use less power, albeit at the cost of FPS. The former scenario would be much more prevalent, however.
Never thought about that, interesting... Thanks :thumbsup: