PSP vs iPod H.264 Encoding Processor Usage

[chemden]

Just an interesting note. When encoding iPod 320w H.264 on a core 2 duo Macbook pro processor usage is nearly 90%. But when encoding for the PSP H.264 the processor usage drops to 52%. The encode for the PSP is noticeably slower. Is there a reason for this??

[Case]

iPod h.264 320w uses the x264 h264 engine.
PSP h.264 uses the ffmpeg h264 engine.
I suppose the difference reflects in CPU usage.