For me it would be image quality first, ease of use means how much time you spend with your camera, knowing your camera, knowing the menu, setting up shortcuts to suit your photography style is utter importance. If you are given a camera you have not used before, it would take time to understand how the camera operates. Or worse, just set it on AUTO mode and shoot lol. To say 6D2 has relatively poor image quality is subjective, people still making great images with 5D Mk1 and the infamous 5D2 regardless the situation they are in. It is how you convey your art and present to the people who will appreciate your style of image. This is where the internet switch into keyboard warriors and things get personal, see what happen to the Canon EOS R thread.