Manifolds are only better if you are into the restostuff or wont pay for a good set of headers. headers make more hp,more torque and may even save you some gasmoney.
saw an adetion of grave yard cars, where mark the wormass squirrel said the old cast hi perf 440 manifolds make as much h.p. on a 440 as headers. he may a lot about mopar, but he`s full of it!!