I don't know if it impact your FPS, but the only difference I saw was in the graphics. You have three different options in Antialiasing: None, Smooth Retro and Antialiasing.
If you chose None, the graphics will have a retro look, more pixelated, to enjoy a retro look to your game.
If you chose Antialiasing, the graphics will look better, non-pixelated and more "clean" appearence.
And if you choose Smooth Retro, you'll get a mix between None and Antialiasing, with a pixelated graphic but a little bit "clean" look.