I own a Viar 450, great quality compressor, thought I would save money and go the Harbor Freight route, it did not last long. I mounted mine under the truck by the running board and installed a 2.5 gallon tank with an air chuck by the running board. You must use a pressure switch with them. Being an impatient person, I bought a set of regulator gauges and a 5# CO2 tank, lightening fast and has an adequate air supply.
All small compressors are a bit slow for me, especially if you are dealing with multiple tires.
The Viair keeps a supply of air in the lines for my air horns. You just can't go wrong with a Viair, quality product.