I rented the G7X and G1X MKII each at lensrentals for 4 days for $75. (And I was very glad I did.) I was considering renting a Sony compact. Lensrentals has excellent service and great if you want to try certain cameras or lenses. I've rented a Sigma f/2.8 50-150mm lens for my 20D from borrowlenses which is also a great service.
So you did the perfect test. live concert with two cameras at same time.... excellent!
I love shooting the g7x in manual mode and the front dial adjust aperture and the rear does shutter and leave the ISO on auto and just adjust the exposure with the wheel.
I love it.
So how did your real world test turn out with a verdict?... obviously the G1x had more detail but when printing I think the G7x and the G1xII are pretty much par for par.