Quicktime vs. VLC, speed

The VLC media player is quite impressive and I've used it quite alot lately since it also now plays .flv flash files. However, compared to Quicktime playing (decoding) h.264 Apple trailer files I have a problem.

I'm running Quicktime 7.1.2 Pro on my PowerBook 1.5Ghz (128 vram), and p720 videos are just about playable (not at full frame rates, but decent still). On the VLC player, however they are unwatchable with lots of missing frames (almost a 'slide show' rather than video...), Even the P480 files stutters on the VLC player, whereas they run flawlessly on Quicktime.

Is the reason for this differences because Apple (with Quicktime) uses the build-in technology of the Apple platform better than VLC? Technology like Altivec and Core Image???