The loudest by far is the aFe Stage 2 Kit followed by the Airaid, with both the S&B and Banks systems being pretty quiet. All of them don't add that much power on their own and their overall performance will be similar until you tune your truck. Frankly, I like the Banks kit the best just because it come with better hardware and couplers than the rest and looks cleanest in your engine bay while being much less pricey than aFe. The S&B kit is a close second, as it's probably the best balance of price and quality. While I don't doubt the veracity of Bank's testing, it's hard to say what that actually translates to out here in the rear world.