<p>I've always been wondering about the actual accuracy of 3D printing devices. When looking for the perfect machine to buy, I looked at the speed, price, filaments supported etc, but also accuracy. I once asked somebody who could give me some advice on what to look at. </p>

<p>One of the things I was told about was that many printers don't necessarily have that crazy precision of 0.05&nbsp;mm (50 micron). Another person told me something different - he said most of those printers actually were capable of putting out 50 micron layer height. How is it really? </p>

<p>Another thing is that the official slicers for those machines also claim that this precision is real, for instance the PrusaSlicer v2.0. </p>

<p>There are many high-end, very expensive machines and even they sometimes claim their resolution is worse than 50 microns.</p>

One of the things I was told about was that many printers don't necessarily have that crazy precision of 0.05 mm (50 micron). Another person told me something different - he said most of those printers actually were capable of putting out 50 micron layer height. How is it really?
Both things you've read are completely correct.
Most printers are capable of 50 micron layer heights. However, layer height does not equal "accuracy" or "precision". The layer height specification is a useless marketing term that you should ignore; layer height is to 3D printers what dynamic contrast is to monitors.
All FDM printers are inherently quite bad at producing parts with tight tolerances. The filament extrusion process introduces lots of variables that are hard to control: the diameter of the filament may vary, there is a delay between feeding filament into to the extruder and it coming out, and the gooey filament that comes out of the extruder behaves in unpredictable ways.
Nobody has figured out how to quantify "accuracy" for 3D printers in a way that correlates with the quality of the finished parts. It is impossible to tell which printer produces "better" or more accurate parts from the specification sheet of a printer.