Thinking about jumping from Nikon to Canon. What am I missing?

Hi, I'm seriously considering a jump from Nikon to Canon but I've read about more people going the other way (and jumping ship from DSLR to mirroless). Am I missing something?

I'm coming from D4S (for sports / track) & D810 (still / landscape) -- both great cameras, and I never considered Canon until recently. On paper, 1DXii looks very appealing relative to D5, and I'm borrowing a 5DSR and getting really great shots with it. I wrote this camera off as MP marketing gimmick but the more I shoot it the more I like it. Easy to get sucked into Nikon has better DR, etc., but DR hasn't been an issue for me on the Canon and -- pixel peeping aside -- suffice it to say can get great shots with either brand. I do marginally like the results I'm getting better with the 5DSR over D810 as viewed normally -- subjective opinion.

So, since I'm of opinion I'll be happy with the shots from Canon or Nikon, things drawing me to Canon are:

1. Usability

After playing around with the 5DSR, I'm now seeing why some people feel Canon has better ergonomics. This is very subjective, but I do like the Canon button layout & menuing system. Coming from Nikon, my first reaction was I hated it but that was to be expected. After only a week, I'm very at home w/ the Canon and do prefer the overall ergonomics to the Nikon. Just me. YMMV -- obviously.

2. Lenses / Mount

I lived w/ A7RII for a few months, but not for me -- yet. I do think mirrorless is the future and Sony is leading the charge. That you can use Canon glass on the A7RII -- and have it work well -- is huge. Starting to see Nikon adapters available (Commlite) but they're not proven yet. Moreover, I assume Sony had a role to play here as well in making the Canon lenses work well.

I don't know what the future holds, but I do know there's a proven system that exists today for Canon glass on Sony -- an that will likely continue to be improved upon. Hence, when I do decide to get a Sony mirrorless (again, with a future model) it's good to know my Canon glass will work with it.

3. Video

I'm primarily a still shooter, but I do occasionally have a need for video and Canon 'seems' more committed to video. For example, 4K@60FPS on the 1DXii vs 30FPS w/ the D5. The 3 min recording limit on the D5 will almost certainly be addressed, but I imagine they won't be able to bump the FPS (just a hunch -- I have no foundation for such a statement).