@mhedges and
@jobrewer1983
My experience and growing knowledge applies mainly to the Sony A7RIII and some other Mirrorless, Full Sensor cameras and the Micro 4/3s. Not DSLRs, I left that tech behind. I got mine May of 2018. All my lenses are native Sony or Sony/Zeiss. I have two zooms and two prime lenses. I'm considering two more Sony primes. They have proven themselves. The stuff is expensive and so I do extensive research to find the best performance and prices. I look 1st for performance, then size and followed by cost. That's my criteria. I want the best possible images, without hauling a boat anchor around.
Nikon and Canon only released their Mirrorless, Full Frame cameras in the last couple of months. They only have a handful of native lenses. So they are limited, for now. You can use adaptors for legacy glass and or third party lenses. But most do not perform 100% and they have varying problems with the new cameras. Nikon just this week updated their firmware for AF Tracking. Sony has had it for some time.
I love the build quality of the A7RIII. It's very solid and compact. It takes awhile to get used to the menu system. Then it makes sense. There is a ton of stuff and it's very customizable. This camera is a professional grade tool. And I eventually intend to use it as such. Right now I'm just learning and having lots of fun.
Don't go on my word alone. There's a ton of great online resources, videos, comparisons and tutorials. Use it. It will help you make an informed decision. If you can get some hands on time.
Just like in audio gear, find what works for you and what you like.