I'm not getting into reccommending that is a whole can of worms! I shoot mainly on my Canon 5DMKIII. Just not found any rational reason to upgrade to the later one yet as it does all I want along with a whole load of stuff I don't need too.
I also bought a Sony Alpha 7MkII to play with on holiday and see what the fuss is about mirrorless. That is a sweet little camera to be fair and would be great for someone who found the likes of the 5D a bit heavy. For me the Jury is sill out on mirrorless but that may just be me not really finding time to play properly.
Personally I think a good quality lens is more important than a good quality camera. On the latter as long as it does the minimal things I need it to do and feels comfortable to use I am happy. there would have to be some quantum leap by one of the makers to make it worth considering swapping out all my glass and changing brand