I'd go for a twin with more flex than an SL if I were you. Maybe a proto if you're looking for a neversummer. Thing is, you won't be riding enough pow or going fast enough while learning next season to require the kind of siffness and damp stability that an SL provides when you're riding 'all-mountain', and a twin will be better for you to practice riding switch while you're still learning. As soon as you get comfy hitting small kickers, it will be good to play around with buttering and little 180's...and the extra flex will make things easier and more fun.
Sorry, but bullshit. Not much difference at all in flex between the Proto and the SL. And the SL is a directional twin and rides switch just fine.