Bicycling

the only stock parts are the frame, cranks and wheels. I'm also a Giant guy and I don't sport a lick of carbon on any of my whips. In any case, your choice should be based entirely dependent the style you ride. I ride a varied terrain of rolling XC with some mildly gnar DH mixed into my routes. Based on that, I'd select the Camber Pro, as it presents itself as more of an all mountain type of bike, while the other two bikes seem more race/XC. At the pricepoint of any of these bikes, the componentry is solid and it really boils down to a matter of grams, so not many concerns on that front. If I were to purchase a new 29er today myself, I'd prolly get either the Transition Covert 29er, or the Transition Bandit 29er, both of which are alu frames. What I'm really curious about is the 640b. Have you looked at any of those?

on edit the Stumpy has a slacker geometry and would be better suited for AM.