I think the Sony FE 90mm macro is sharper. Insane sharp as some mentioned.
If you go here:
http://www.dxomark.com/lenses/launc...ewMode=graph&xDataType=year&yDataType=effmpix
you can see all tested lens by DXOmark, scroll down and will see a graph, showing the sharpness and which is better.
About your second question -
I am using Sony A7R II + Sigma MC-11 + Canon EF 24-70 F/2.8 L Mark II - I use this combo for my professional shoots all the time and I am very very happy.
Two negatives:
- when the light is dim it hunts a little. Get another light source, LED or something else - problem solved (I am shooting models, so the solution is ok for me)
- not the best combo for fast moving subjects. I tried it on the Wembley moto stunt festival - it works good, even in AF-C mode, but the tracking on A7R II + Sigma MC-11 is not the fastest.
Besides that combo it deliver. A lot.
So I will stay with the Canon version. Sure the Sony option will deliver better focus speed, but for most of my work i am happy.
Example from Wembley stunt festival:
Ace Cafe London Stunt Festival & Streetfighter Show 2016 by
Kalin Kalpachev, on Flickr
P.S. There are so many choices of camera/lenses these days that sometimes we don't know what to choose or buy. So many temptations.
But. the truth is that many cameras/lenses will do the job - just pick one, go out and shoot