A question for those of you with experience across machines: Do two machines with the same kind/power laser (e.g. 20w diode, 50w CO2) cut similarly?
I wonder, in particular, if I find recommended settings for one brand 10w Diode laser, whether I should expect those settings to work on another 10w Diode laser.
And a related question: Any recommended sites/videos for how to -evaluate- test results for cutting?
It is extremely rare that the machines and conditions are the same, therefore (my) answer is, no.
I also consider my own material libraries only as indicative starting parameters, which have, however, at a given time and for a given material, fitted perfectly.
For cutting operations, there are often no problems because the power settings are in a “safe” range that should compensate a little for fluctuations in the surrounding parameters.
When engraving filigree things like pictures, it is a little more complicated. The grayscale does not allow a plus/minus 10% margin, here I (also) test everything to see if my library values ​​still fit. It is a bit of work but saves me a lot of material 
Generally speaking, if both of the lasers emf is absorbed in the same amount by the material for each machine, then you should have similar results.
It really doesn’t matter too much about output power as it does emf wave length. A blue diode will have more difficulty than a green diode engraving blue acrylic. Neither will work well on a clear material.
@bernd.dk is speaking from experience and it’s wise, I’m giving you the science. There are so many variables that there is rarely a direct match, more of a ballpark value.
Without any experience with CO2 machines, but with what I’ve learned so far about laser machines, I dare to comment.
Sometimes, even with precisely identical machines, side by side, you don’t get the same results.
The result of a job, whether cutting or engraving (engraving is more critical), depends on several factors and not just the power and speed of the laser.
Issues such as temperature and relative humidity of the material are two of the factors that most interfere with the final result, especially in organic materials.
In my opinion, and in line with the opinions already given, I would say that under laboratory conditions it is likely that you can achieve the same results. Otherwise, only similar.
However, and it depends on the person, what I consider a small defect may be perfectly tolerable by another person and vice versa.
I apologize for intruding, but I believe I have something to contribute to the question at hand! 
