I still couldn't believe that difference so I got VLC to run and tested on a 2 minute sample. (Note: CPU time includes startup cost)
VLC:
8-26%
15% avg.
17s
MPC (w/ CCCP):
18-36%
27% avg.
37s
I also searched for any ways in which VLC may "hide" its CPU usage, but didn't find any secondary threads etc. So I believe it is fair to say that VLC is actually nearly twice as fast as the alternative.
However, there are a few facts that need to be mentioned to qualify that statement:
- VLC did not show the softsubs correctly
- Even in the short sample I tested it bugged out in one instance (totally)
- Most importantly, why would I care if playing a clip uses 15% or 27% CPU? And my system isn't even fast by todays standards (2200 Barton)
My conclusion (note that I have no particular stake in this "war"): If you have a very slow system, only watch hardsubs and get lucky with the encodes VLC is a good choice.
(That is, if you can stand the interface which is quite horrible IMHO)