The C100 is an AMAZING camera. Very underrated. Awesome image and interface. It's closer to the Alexa than to the 5D Mark III. Resolution is great, colors are beautiful (if warmer/less accurate/more subjective than the Alexa, they're certainly way better than Red), and the interface and ergonomics are great and the battery lives forever. It's the prefect owner/operator cinema camera. One person can use it easily and yet the image quality is approaching other high end cinema cameras. It can be set to intercut with dSLRs, or used as a b-cam for the Alexa with an uncompressed recorder. WideDR mode has Canon Log levels of DR but in a linear space. The specs (AVCHD/8bit, etc.) are poor, but despite that it's great. It uses superwhites (watch these in post) and a wonky log curve to retain decent tonality despite the poor spec.
That said, DR is still not the C100's strength. It blows away dSLRs but it is not as good as the Alexa, F3 (though only a half stop away, though, from the F3 with slog and ACHD beats XDCAM, seriously), or Red with HDRx (it's, imo, on par with Red without HDRx, maybe better). Really only the Alexa has amazing DR out of the box. I haven't used the BMCC but my guess is it's decent, maybe better than the C100 in this regard.
The question boils down to if you want to do more work but have more control (BMCC), like if this were your hobby or if you wanted to do less work but have to do it right int he fist place (C100). It reminds me of the "pros shoot JPEG" mentality, but that's kind of how it is. The C100 can provide gorgeous footage but you need to be a competent shooter. With RAW you can do all sorts of dumb stuff (overexposure, WB shift) and salvage it in post, but that's so much more work.
In normally lit rooms during the day it holds highlights out the window way better than a dSLR, but worse than the Alexa. You might need to turn some lights on (bring in daylight balanced CFLs or something) or choose your angle and exposure carefully, but if you're a competent shooter it will blow away your dSLR. Unfortunately it's superior more for tonality, noise structure, reduced skew, color, etc. than for DR, but nonetheless it's in a whole other league from dSLRs without being more difficult to use. Love this camera.