Originally Posted by fore
Even if it does work, the SRAM shifters lack a trim option when in the big ring. The design of the outer cage plate on the SRAM deraillers prevents rub across the range of the cassette. Switch to the DA derailler, or any Shimano, and you lose that, and gain a bunch of chain rub.
The way I see it, the Force derailler is cheaper than the DA, and the Rival even moreso. Unless the OP already has the DA derailler laying around and wants to put it to use I see no reason to pay more for the Shimano when they can just buy the appropriate part, save a few bucks, and be assured it'll work as designed.
this would be a new bike, so i'd just be swapping components. the DA fd would already be on there, but you're right, a rival or force fd is pretty darn cheap too... in case it doesn't work.