IMO, the only trait that a bi-pod offers that is better than what a good set of sticks offer, is the fact that sticks can't be left behind, they go where the rifle goes.
Once a guy uses sticks and gets used to them, rarely will he go back to a bi-pod for calling predators. If I were sitting, or laying, and shootnig targets that don't move or don't move much, then I'd pick the bi-pod fixed on the rifle.