With any cold air induction kit, plastic has the benefit of running at cooler temperatures than metal. Aluminum is a bit better than chrome or sheet metal intakes, as it disapates heat quicker. Which will run cooler between plastic and aluminum ? I'm not entirely sure, but I'de probably guess plastic by a notch or so. Something also to be considered is the casting of plastic intake tubes tends to be smoother than most of the metal ones, so the smoother, the better in terms of air flow.