Firestone and AirLift both have their claims as to which is better. When I bought bags for the GMC I went with AirLift.
Mostly because of the attached PDF file.
I also used the AirLift wireless kit, which is a great addition, especially for my application. Just to get out of my driveway I had to dump all the air. Once out and heading down the street I pushed a button to a predetermined amount of air.
I have not decided yet if I will put air bags or some sort of air ride in the new truck. If it is bags only it will be an AirLift kit. Customer service is very good.