The biggest difference is the visibility of the layer lines.
No matter what quality level you choose, you will see visible layer lines in FDM. At a higher quality setting, you may see them less and they may be easier to smooth out in post processing steps after printing. However, printing at a higher quality setting means it takes longer to print.
In SLA printing, layer lines are typically less visible than in FDM. Printing at a higher quality setting in SLA means that your parts will appear with virtually no layer lines. As is the case with FDM, SLA also takes longer to print in a higher quality setting.