[Brightcolours]

 

 

But speaking of the lens at hand, if I had been into the long teles AND mirrorless, I might've looked at another 100-400 instead: the Fuji one. The results seem a lot more harmonious there (at least from the Lenstip tests).

True, but you do have a reach difference due to the crop factor. 

With the "Leica" you get the same reach at 300mm as with the Fuji at 400mm. Then the comparison shifts a bit more to the positive for the "Leica"?