Choosing an air compressor is not a light subject. This can be an expensive purchase, and an unwise choice is costly and frustrating. This is not an item for "cutting corners" or bargain shopping. You will get what you pay for...
When I needed an air compressor for the magazine's shop/studio, my thoughts were about air tool operation. My previous shop was well served by a DeVilbiss 80 gallon upright compressor and a quality black pipe system. That compressor was a two-stage (not "twin stage", avoid these!) iron compressor model that ran on 230V. Bought it in 1995-96 timeframe from Costco for $800.
Our new, smaller scale shop/studio, I thought, could get by with a 20-gallon upright portable compressor and an iron, two-cylinder unit compressor head (two-stage, of course). The Ingersoll-Rand 'Garage Mate' fit the specifications I wanted, and that purchase proved wise—initially.
There are jobs that require high volumes of air, and one in particular is bead blasting. The smaller compressors, you will discover, often make higher output ratings by running the compressor's rpm up the scale, to the point that service life becomes an issue.
The DeVilbiss unit, in fairness, held up in this category with its 7.5 HP motor. (The I-R Garage Mate gets used so little that it should also last "forever".) Horror stories about sucking a reed valve on the DeVilbiss never happened, and that unit served faithfully for fourteen years—it was still working fine when we sold the shop property and the complete air system stayed at the shop.
When I discovered the need for another bead blaster (had one at the previous shop, a very nice T-P Equipment unit), I thought a smaller unit would work fine with the Garage Mate compressor. It didn't. After much research and study, I realized that volume is everything for blasters, and my quest turned up a terrific solution: a used commercial compressor with a huge, slow speed Champion R-15 compressor head, 120 gallon horizontal tank, and a 5-horsepower, industrial strength Baldor 220V motor with magnetic starter.
If you'd like to know more about this compressor, and perhaps what amounts to my sense of humor, read this account at the magazine: http://www.4wdmechanix.com/Downsizing-and-Air-Compressors!.html. For $250 less than the new I-R Garage Mate cost, I'm in business and so is the bead blaster!
There are values like this around if you'll look and be patient. The Garage Mate works fine for quick, shorter burst air tool chores or inflating tires. I'll keep it, as the resale price is ridiculously low, and the unit is in "as new" condition.