Technically, both shoot 10bit but the C200 is really going to be an 8bit camera for 95% of the people who use it.
Slow-mo raw shooters can now make use of an improved 2K 60p mode on the 5D Mark III thanks to Magic Lantern.
In addition, 1920 x 800 recordings at 60fps are continuous to the card without a frame limit, a feat made possible thanks to new lossless compression.
What do you upgrade to once you get bored of Sony and Panasonic?
I went to find out.