it depends a lot on what you are going to be working on cars and lt trucks i would go with an ir 231 any thing bigger is going to need at least a 3/4" impact or a 1"impact
I like my older blue point, I don't even know the model number. I changed the bearings in it and it works very well. I also have a 3/4" drive HF earthquake that is loud, but works well so far.
The Cornwell CAT4150...great wrench. This is also the Napa 6-1123. Strong, light , ( just under 4 lbs.) and the shortest 1/2" (full sized ) composite I can think of. One of my favorites for sure. I would make sure whatever you get exhausts out the bottom of the handle, the IR 231c does not, it's out the front. IR 231H,and 231HA exhaust out the handle and can be had with extended anvils as well.
Most important thing about shop owned air impacts at a tire shop is that they can take abuse. And those things have been proven to take any and all kinds of abuse for years, powerful and cheap to buy too. Shop owned tools will be abused and not maintained.