U need to decide exactly u are looking for. Your post suggests u want smthg thats easy to get into, go for a blast have fun and then park it back in the garage without much hassle. The SLS is gonna be pretty much that (although no manual, but then the slushbox will tick the easy/comfort tag again) plus it will oversteer till the tires are finished, sounds fantastic, and has those awesome gullwings. On top of all that depreciation has been a killer for new owners (atleast in europe it has, im guessing same in USA), so pick up one with 3-5k miles, with Merc warranty and you are set.
Oh, and keep the SV !