I've never used either of these, but a close friend of mine whose an amateur boxer raves about Cardarine (GW). However, there's still the whole "cancer thing"
With AICAR, correct me if I'm wrong, but didn't the studies on mice determine that it only showed benefits (insulin sensitivity and glucose uptake leading to more energy and fat-burning) in the obese and out-of-shape mice. I believe the studies found that the healthy mice experienced no benefits from AICAR. So, depending on what kind of shape you're in, I'm not sure how beneficial it will be for you.
I also believe there were some issues with AICAR as far as enlarging the heart and something to do with damaging the brain or something. But I could be wrong about this, so you might want to look into it before using.
