Looking for air intake system to improve mileage  or are they equivalent?  

Air intake systems have gotten a lot better, even from the OE standpoint. An aftermarket intake will probably give you more of a power gain than a mileage gain. The bigger factor is driving habits and vehicle maintenance. Regardless of what anyone might claim, nothing's going to give you a 10 mpg increase. But a combination of properly-inflated tires, regular oil changes, transmission & axle maintenance, and a tonneau cover, as well as driving more conservatively will probably give you the best results.