had several of my PCB enclosure halves end up pretty significantly thicker (on the part that was against the build plate) than I designed them to be.
The plate is not level.
If it was the base thickness would be even and consistent.

As far as the appearence of fdm parts go - they can look pretty damn good. use 0.1 layer height and the right filament and the layer lines are pretty much impossible to see. Some of the new pearlscent filaments are excellent at hiding layer lines.

As fara s strength goes - that is very much down to the resin.
Formlabs swear that their resins are a leats as good as fdm prints and they even have flexible filaments.
But they are very expensive.

So benefits of resin versus fdm.

Fdm:
cheap
very little post processing
really versatile - different filaments and nozzle diameters give a phenomenal variety of print parameters and qualities
machines are easy to self service and modify

resin:
capable of really clean high resolution prints

I would say that unless you are making small models like dnd figurines or have an unlimited budget, fdm is generally always going to be better.