Just about all air compressors come with an air pressure regulator, so you can run up the PSI for those air tools you use, and lower the psi for duties like blowing dust around or pumping up tires in a bike. What you really need to be wary of are volume and storage. Personally, the more volume you can practically store, the better. I have a 30 gallon unit and it can run all my air tools from a nail gun to my impacts wrenches and air hammer. To run tools like paint sprayers and impact wrenches, you need lots of volume, at least 25 gallons worth of air for most air tools, and maybe 50 or more gallons for paint sprayers to maintain a constant spray pressure. But for things like a nail gun, you only need a 1 or 2 gallon unit.
However, if you need to drag your air compressor to somewhere like a roof or through doorways and all around, make sure you have a wheeled unit or make sure it's small and light enough to take around with you.
So consider how you will use the air compressor (just nail guns and occasionally pumping up tires? Or any intense use like paint sprayers or impact wrenches). Consider where you will use it (In the house? Garage? Roof? etc...). That will help guide you into selecting the right compressor for you.
E'Aho L'ua
2013 RAM 3500 Crew Cab 4x4 SRW |Cummins @ 370/800| 68RFE| 3.42 gears
Currently Rig-less (still shopping and biding my time)