Sure, it's cheaper! The images look good, and I see nothing in the image of the C100 worth the extra price. ND filters for $2,500? In return I get 60 fps and the phenomenal E mount.
I don't like the look of the C300. DR I don't care about, if at the end it still looks like video. And I shoot with L zooms and Zeiss CP2 primes. The ergonomics suck. Why do I use it then? Because I only have to pay about $180 per day for everything! My lighting bills are lower and I get a great codec for native editing.
If it's a choice between the 5D and C100, I'd choose the latter if budget isn't an issue.