Hi! I have switched from M85 to Samyang 85 1.4 and the short story is like this:
M85 is smaller, nicer to touch it and in some conditions something like magical
.
The Samyang - sharper wide open with less fringing then even top class lenses like Canon 85 1.2, Nikkor 85 1.4, Sigma 85 1.4, Nice and smooth render but sometimes when the magic of the M85 appears the samyang is a little boring without any bokeh only defocus. And the samyang renders colors much better. About sharpness - M85 is sharper from 5.6 to 11 a little more but only a little.
And the samyang is a little wider like 83mm or the M85 is actually 87mm.
The focus with the samyang is much easier when focus on distance but it appears that focusing the resolution table is another thing
I didn't succeed to focus with the samyang better without liveview.
I have head to head comparison in bokeh but it is in PEF on my HDD and still not uploaded... no time for this.
Here is something that is impossible to be done with M85: