The average CPU usage was slightly higher when running MPlayer with GL2 video playback under Ubuntu Linux. However, on Ubuntu most people end up using at least X-Video if not XvMC, VDPAU, or VA-API when using MPlayer, which results in lower CPU usage. On Mac OS X, CoreVideo often ends up being used.
Turning to more of the computational tests, MP3 encoding performance was about 8% faster with Mac OS X.
The video encoding performance through MPlayer's Mencoder was also faster with Mac OS X.
Ubuntu 10.04 came out with a win when it came to dcraw that measures the time to convert several RAW images to PPM.