The prime is sharper and the micro-contrast is excellent, I mean, the GM is a zoom, it's excellent, for a zoom, but it's still a zoom.
There's pro's and cons to primes and zooms, I mean, you can shoot with the Batis 25/5, 55/1.8 and Batis 85/1.8 and replace that GM...
You can do the same with the GM to replace the primes...if you weigh all three primes they probably weigh as much as the GM...lol
I guess what I'm saying is that there isn't that much difference in IQ, it just depends on how and what you are shooting and how you want to approach it.
I know from DXO that my Batis 25 is sharper than my 24-70 GM...But I can't really see it on the screen when I zoom in, I mean, they both look sharp to me..
The 25 is awesome, I like it better than the Batis 85...I think the 24-70 GM has better bokeh than both of them though.
You want a very very sharp lens and with beautiful Bokeh as well? get the 85GM