Wait... are we debating about a 2.5K 12-bit RAW camera with a 5D Mk.3? Am I not seeing something? Im not entirely the tech guy when it comes to this stuff, but the 12-bit RAW alone sold me on this camera, no more gimped color space. The only thing the 5D had going for it was its low light and full frame. Two of which are not that important to me, using the high iso of a 5D seems like a last resort kind of thing. 2.5K is perfect for 1080p video, alot of leg room if you need to crop or stabilize shots in post.
Im sorry but looking at the footage of the BMCC, it looks quite phenomenal to anything ive seen from a 5D. Am I not seeing it correctly? I loved the grain as well, its not what you'd get from a GH2 or 5D, which is more purple square blotched noise then film grain.
This is my thought, you get 2.5K with good RAW codec and 13 stops of dynamic range compared to a 1080p (which could be questionable if its 1080p) soft image(which can be sharpened in post) full frame camera. Both around the same price? You'd be mad not to got for the BMCC! Its the obvious choice! No more recording limit, more input/output options.
Either we're really nitpicking here or im just not smart enough to see the bigger picture.