I would just buy the official one. The generics may work, but you are greatly increasing the probability of having config problems, plus they are only of spotty reliability (check the reviews for 3 stars and below on those). For $7-9 less than the official adapter, I wouldn’t bother.
Just my opinion, but one formed around some general research on what works best “out of the box”, which is why I’m not going with a PS3 controller and bluetooth dongle. Lots more “help me” posts with those than the 360 controller, which seems to enjoy a more stable, preconfigured setup as a whole. I may be very wrong about that though as all the underlying software keeps getting better and better!
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