The MX Master 3 is a wonderful piece of hardware but I personally couldn’t get used to it. I find the Magic Trackpad, though obscenely expensive, seems to fit my needs much better. I used the MX 3 for about a year. I do love some features it has.
If you're a hardcore mac user, I would agree, and even then if you like using trackpads in general. I switch between mac and linux all the time, plus I found using even the MBP 15"'s massive trackpad annoying to use for all-day work, so the MX Master was among the best investments I could've made.
The wheel on the MX Master is brilliant. It’s hard to leave that behind. I think the only reason I couldn’t stick with it was that I need to pan and zoom so often, and the pad makes it so much nicer without compromising too much.
I don't think I have ever cared about how my mouse looks (or how my laptop looks for that matter; it sits at home where no one will see it).
Something you use 8 hours a day should first of all be pleasant to use and reduce the risk of long term damage to your wrist (carpal tunnel syndrome or similar).
I've never found the Magic Mouse uncomfortable to use. I generally use a trackpad anyway. I value that it's portable, looks nice, and works great with OS X. To each their own.