When making a large purchase such as a compressor, it should be made with full knowledge of what you are buying, and the least expensive or most expensive might not meet your needs. First thing to look at is the motor.. Not all 5 HP motors are the same. Today, the manufacturers have ways of calling a 5 HP motor that truly isn't 5 HP. I liken it to the number of plies of a tire.. They used to be the actual number of plies, but today, you can find tires that are 4 ply rated, but are actually 2 ply tires. Getting back to the compressor, the manufacturer of the motor is important since if you want a true 5 HP motor, you will immediately see the difference in the size. A true 5 HP motor will require an external magnetic starter box, where as a 5 HP rated motor will not. The same with the compressor itself, as has been pointed out, you will be better off with a 2 stage compressor than a single stage compressor. Inexpensive compressors, even 2 stage inexpensive compressors will have splash lubricated bearings, where the more expensive 2 stage compressors will have pressure lubricated bearings. Next thing is the question of brands of compressor, not who's name is on the tank, but the company that actually manufactured the compressor itself. There are a number of good compressor manufacturers out there, but the one thing that is important, is where was the compressor manufactured.. in the USA or China. If made in China, you might not be able to get parts for it in 10 years if you should need them.
I have 2 Quincy brand compressors, one is a 5 HP Baldor motor mounted to a 80 gallon tank and a 2 stage Quincy pressure lubricated head with an oil filter. At the time of purchase, I also specked that I wanted the ability to have it a continuous run or stop / start run motor. This is accomplished by the twist of air operated valve switching the motor control box from continuous to pressure operated. When the tank comes up to full pressure, it opens the valves on the compressor head, and bleeds off the air being pumped. This allows the motor to continue spinning so when I am using a lot of air, such as sandblasting, and the tank will replenish the air more quickly. I purchased it in 1995 for $1500 new.
I also have a Quincy QT54 that I purchased at a salvage store. The compressor came with a 3 phase 3 HP motor, which I replaced with a new 5 HP Baldor motor and magnetic starting box. This is a splash lubricated 4 cylinder reciprocating Quincy head. I purchased it inexpensively but buying the motor and starting box, cost more than the purchase of the compressor and tank. Probably a bad decision on my part, but I can live with my mistakes. All together, I am into it for about $800.