Yes it is....thats why I UPGRADED.... Image Quality, low light shooting (where it focuses much better than a 7D) are what is important.
...what is important to you. I think you forgot to add that part. For someone with a 7D who shoots fast-moving sports, birds in flight, etc., would the 6D be an upgrade? No. A better sensor for low light doesn't help if the AF system can't track your subject...you'll just get low-noise blurry shots.
As I asked elsewhere, is a Mercedes SL550 convertible an 'upgrade' to a Ford F150? Not for someone who needs to haul around loads of dirt or bricks every day...
Can you honestly say the outer AF points of the 6D perform better than those of the 7D?
Well to be honest I did not buy the 6D for its outer points performance, no one would I read the specs and knew what I was getting. To date I have not had any major issues with the focusing points although I do concede that the 7D is far superior in most respects on focussing - apart from the killer 6D centre point
I loved the 7D it was a very capable camera, its just that the 6D takes better pictures.
As I said I did not use the high FPS at all - how often do you use it ?
I take a range of pictures from Macro, portrait, landscape - although the &D was a great camera, top of the range APS-C camera, I do not believe that it is as good as the 6D - bottom of the range FF camera.
I use the 600ex-rt system - the 6D has additional features with the RT system that the 7D can't do - one of the reasons I bought it.
The WiFi is no gimmick and for remote untethered shooting and the ability to display images in the field on an iPad once again a feature I really wanted.
Lastly and most importantly I wanted to go to a FF sensor.... something the 7D is nt - I could not afford a Mark III which is far superior to the 6D.
So all in all the 6D afforded me the upgrade path I wanted!!