I know the 5D3 beats the GH3 for depth of field, but what about actual still image quality? I'll be doing food photography at the wedding for which I won't be making large prints, just for the web.

Has anybody here used both the GH3 and the 5D3 who can post their experiences/examples?

Thank you. :)

5d should be miles better for stills. But I'm sure the GH3 would be just fine for your purposes...

The Canon is a full frame, professional camera. The GH3 is a high end consumer camera that can take professional quality photos. There is no contest, Brian is correct and what he says is exactly right. For your use, the GH3 will be fine. In the right hands, with the right lens, the GH3 is no slouch, but cannot touch the Canon.