I just got a new 4k camera, a Sony HXR-NX80.
I uploaded 4k footage, 1080p footage in both XAVC S and AVCHD and my original Canon HF G30:
All shot with my usual lights and shooting conditions, direct upload, no processing.
4K:
1080P60 XAVCS
1080P60 AVCHD
Canon HF G30 1080P50 AVCHD