I have three cameras, this is how I mainly use them:
- I shoot events and sports with my main camera being a 1DXii,
- I shoot portraits with my main camera being my 5DSR
- I shoot nearly everything else with my A7Rii and a Canon 24-70 F2.8
My major issue, and the only major issue I have with the Sony A7Rii, and now A7Riii, is that if you are going to be working for hours with a camera in your hands, that Sony camera needs a grip (at least for my hands) - and I can learn to deal with the smallness of it besides the grip.
I say this with all honesty, this new Sony, if it had 85% of the ergonomics of a 5D4 or D850, Canon might not sell another 5D4 - why?
- better sensor
- EVF for metering / exposure
- Eye/AF
- silent shutter if needed
The fact is, Sony is going to sell a crap load of these cameras. I will most likely trade in my A7Rii for the new one, but for me personally, I need really good ergonomics if I'm going to work an event - but if it isn't an event, then the new Sony will take it - and now I think even the 5DSR will get sold.
If I was a Nikon user, with lots of Nikon glass, I would buy the D850 - otherwise the A7Riii is going to start to do real damage to 5D4 sales in my opinion.
shooting a 24-70 is a two handed operation, is it not? You have to zoom in/out, and cant ham it for any appreciable amount of time.
. Are the sensors from Nikon/Sony better ? Of course they are ! That doesn't mean Canon is now garbage ?
It has nothing to do with "brand loyalty" either...not everyone can afford to jump ship once heavily invested in a system. 

