I've just been getting started with FDM printing since this summer, and after getting to know the limitations of my printer I'm even more amazed at the smoothness and resolution that some resin printers are getting. (I've even heard of people starting to print optical lenses[0], which I can hardly imagine.) You can really see the difference in resolution in the image with the different bottom shell!
I would have assumed some post-processing would be necessary to create a polished surface, but what really blows me away is that it's possible to make the entire interior void-free and consistently dense to create a transparent lens with no air bubbles or interior pockets. I can't even do that molding resin by hand.
0: https://www.cuddleburrito.com/blog/2015/10/13/3d-printing-vi...