Having shot on the BMCC, it depends what I wanted to do.
BMCC footage looks good and a good example of what I have done is here:
https://vimeo.com/paulrwalker/review/84971935/ccf932163f
BMCC is great at music videos, commercials, film making or VFX-heavy environments. The RAW codec at 2.5 gives a ton of flexibility in post and that means better quality and lots of good things. With prores, irrespective of how flat it has been shot, we simply could not have pulled the colour around, composited or blended a little VFX in the way we did above.
In terms of inserting VFX / compositing, the BMCC's codec gave us the ability to do whatever we wanted in post.
The Canon is a good camera but simply does not do that. However, without the crew (e.g. the little datacenter we had running in the background), or in an environment without backup, easy access to lots of cards, power etc..., then we would've taken the Canon.
Different tools for different jobs.