I was in the same boat once, torn between those two. I ended up getting the Evo because overall people said it was a funner board thanks to the greater flex. Part of the reason I got it though is because I already have a board that is probably similar to the flexiness of the SL, an older Atomic Hatchet. This board is classified as an all-mountain park board, but it's quite a bit stiffer then the Evo, and I've been using it as an all-mountain board for a long time.
So if you already have a board that fits that stiffer ticket, I would grab the Evo because then you will have a choice and will have the best of both worlds.
If this is going to be your only board however, get the SL because it will be more versatile.
I will admit that while the Evo does really shred everything, it does not like chunked snow/powder because of the lack of dampening, so if you ride in a place that's not groomed terribly well all the time or ride crapped up powder, the Evo is going to throw you around.
PowderHound and TreeNinja
Last edited by HoboMaster; 11-11-2010 at 08:00 PM.