IMHO, the very best air tools are as follows:
1/2" Impact Wrench (pistol style) = MAC Tools
3/8" Impact Wrench (pistol style) = Snap-On
1/4" Impact Wrench (pistol style) = Snap-On
3/8" Impact Wrench = Snap-On
1/4" Impact Wrench = MAC Tools
Die Grinder/Cut-off tool = Snap-On
1/4" Angle drill = MAC Tools
3/8" Angle drill = MAC Tools
As an ex-mechanic (of 7+ years at the dealership, 2-3 at the local garage), there's no comparison between these and the over-the-counter air tools. I know that MAC uses IR/CP for some of its tools, but they seem to do a better job with housings, etc.
Expensive, but it's nice to only have to buy one and have it work well the first time and everytime.
Oh, and the key to long life is maintenance - buy some quality air tool oil & if your tools are greasable, buy some quality air tool grease. I prefer Snap-On's air tool oil and MAC's grease.