As a mechanic I have used IR for years ...I have a variety of air tools from IR, MAC, Matco, Snap~on....etc.
My favs are IR...I worked with a guy who has a protoype IR231 from 1966 and still going...that's tough stuff!
The IR or Mac composites are really light/quiet and can hit plenty hard.
I recently purchased a MAC 1/2" DR. composite gun tha hits @ over 900ft lbs.!!! I pulled the budd nuts off a heavy truck with it !!!
As far as the field an air compressor just isn't an option when wheelin' so I have an 18v Snap~on 1/2dr impact, flexhead flashlight, reversible drill. I crew for a Primitive Racing(rally) and these are essential tools.