scroll down to "Discharge Rates" illustrates the effect of capacity offset
If you look carefully the Phoronix results it is visible that Ubuntu don't have any power budget cap and OS X has. The power usage under Ubuntu is jumping all over, but OS X is much flatter. Apple has implemented power cap on kernel level. And I am sure this is because Apple had set battery life as priority. Other manufactures have other priorities like better performance. I think this opens opportunity for other manufactures to distinguish their offerings from the competition.
The BSD/Mach memory management backend on MacOSX throttles more of the major processes when compared to Linux's allot and swap scenarios.
The schedulers are vastly different. BSD/Mach seems to handle heavy loads where for a long time Linux's standard practice was to cease up until the task was completed.
My facts are only seen by the individual who is willing to install both and witness for themselves.
Copy a Nine-Gigabyte file from one folder to another. Applications will still open on BSD/Mach. Within Thirty seconds you'll be unable to do anything on Linux.
File-systems can also request a large amount of processor power. But it's up to the memory management and scheduling to throttle that request down the queue.
I for one will be glad when Torvalds, Molnár, and crew go to Best Buy and buy a consumer model PC and witness for themselves what everyone has been putting up with for 10 years.
Scheduler arguments are a lot like religious ones.
What your benchmarks suggest to me is that maybe Apple is purposely capping the maximum wattage for battery life/thermal reasons.