Likewise I have a post about testing lpi limits in baltic birch; your results are inherently tied to your material.
Each material will have a maximum possible resolution that you can engrave beyond which higher resolution just won’t get any better result.
Also I can see how the dithering routine in dots would be highly affected by the source DPI. I almost always use vary power when engraving and so it’s probably not apples to apples… the exception being on tile. Dots gives me a better result there, YMMV.