🚀 go-pugleaf

      Would optimal space usage be a good argument for using VBR instead of
      CBR?




There will be little, if any, difference.
VBR works by assigning 3 values:
Target, or average bitrate
Maximum rate
Minimum rate
It is generally used when the desired average bitrate is lower than what is needed for optimal quality, and it works by encoding some scenes (with little or no motion etc) at a lower rate, thus building up a pool of "saved" bits for complex scenes.
The space on a DVD is finite, otherwise we would simply encode everything to CBR at the maximum rate allowed.

Final space taken up by a VBR file will be the same as a CBR file.