A long time passed.
I did not follow it and could not respond in time.
Now it is closed and I can not write there.
I do not know whether I rightly publish my belated answer here ..
I think my answer will be relevant here.
If not, then moderator, please correct me.
https://www.keyshot.com/forum/index.php?topic=10396.msg52340#msg52340@Frody
Would it be possible to share your KeyShot renderings?
Can you share the model you used to render in Bunkspeed?
It would be great if you could help us match your results as close as possible. 
I did some quick test rendering in KeyShot 6.
What do you think?
Dries
Hi Dries!
The material has become much better than it was in the previous versions.
But still needs to be finalized
All the same, there is a certain amount of turbidity and lack of detail.
At a low ABBE The colors mix with each other incorrectly. They do not correspond to the laws of physics.
Herein lies the main problem of not realism.
Below I am attaching two projects of the same product in different programs (Bunkspeed is now SOLIDWORKS Visualize) project in this program.
The material is configured the same. To see the problem at a low level, I lowered the number of ABBE to 5. The same HDR.
In the KS renderer, you can see that the blending of colors does not match the color spectrum. Hence all the problems follow. For example, between blue and red flowers there is dark purple (very dark almost black).
This does not happen in reality. This error is always present.
In SV there is no such problem. Colors are mixed correctly according to the color spectrum.
At any ABBE, the diamond always looks right. For any ABBE diamod always is clean. No dirty yellow and dirty brown.