I have been using my 5D3 for awhile, and recently purchased the new G30.
I will be converting both to ProRes and importing into FCP7.0.3.
Which would be the best setting on the G30 to capture highest quality image to match with 5D3.
On occasion I also use a T4i as a Bcam.

Re: G30 - I'm not completely clear whether AVCHD or MP4 yields best result...?

I have been using the Beachtek DXA XLR-PRO with good results, that's why I didn't buy the XA20.