haven't ridden the devinci, but the rocky is insane. very tough, climbable, great descender. i've ridden several at demos and from our shop, and can say that i'll definitely (finally) be riding one next year.
I would go Devinci for the Slacker Head Tube angle, Horst Link Suspension and good bang for the buck.
The 09 rocky gets a copy of the Horst Link but avoids the Specialized patent by having the pivot 5mm above the rear axle. Would be interesting to see how much that effects the wheel path...
slayer all the way, i ride mine like my hair is on fire and the slayer asks, "is that all you got?", plus im 200lbs, so you know im not all that delicate on my gear
I haven't rode the slayer but I do own a '07 hectik 2 and I love it. Its very pedal friendly and light for a bike that has over 6 inches travel front and back. Its also very strong and jumps like a dream, I know guys that have full on freeride bikes that have tried mine and now they want to switch because it can do anything thier bikes can do but the hectik pedals up hill so much better.