utils is large enough without these compatibility functions.
Everything that is present in newer versions of Python (i.e. with dev Python it's just an import) goes into compat.py .
Everything else (i.e. youtube-dl-specific helpers) goes into utils.py .
Affects the ffmpeg post processors, if ‘--prefer-ffmpeg’ is given and both avconv and ffmpeg are installed, it will use ffmpeg. Otherwise it will follow the old behaviour.