[I find this debate very interesting]
(only simple playback of h264 movie with 2 audio tracks. My hardware is from 2011)

My results with X11-openGL:

With CIN_HW_DEV=vaapi ./cin --> CPU 67% (error in terminal)
with CIN_HW_DEV=vdpau ./cin --> CPU 60%
without vdpau or vaapi      --> CPU 67%

[Remenber results with X11 --> direct rendering on:

With CIN_HW_DEV=vaapi ./cin --> CPU 60%
with CIN_HW_DEV=vdpau ./cin --> CPU 11%
without vdpau or vaapi      --> CPU 60%]