They do something... Help make noise lol. An aftermarket intake helps, but for the cost are they worth it? Not really, esp on an otherwise stock motor.
Between the 2, CAI is a little better for power since it's bringing in cold air but if you were to compare the 2 directly just driving down the road, I highly doubt you'd notice any difference at all. You just need to be careful if you drive in an area that floods with a CAI. You don't want to drive through a large enough puddle that you submerge the intake and destroy the motor.