John is a superb wildlife photographer and I've known him for several years. The big game changers for him are the light weight and quietness of the R5, because he spends a lot of time on foot. He's used to using the toggle for moving the focus point around, and he doesn't use back-button focus. I for one just can't stand the toggle, and I love using back-button focus. So the 1DX III with the trackpad AF-ON button is the biggest game changer for me personally. If they ever incorporate that into a R5 Mark II, I would be all over it. Till then I will keep the lowly 1DX III and put up with it somehow . I don't mind the weight or the "low" MP count. If you really need high-quality files for big printing, the Topaz software (DeNoise and Sharpen) do a fantastic job and turn your images into something that you can pixel-peep with great satisfaction.