Seems like it depends also what you want for a working psi ...... here is a quote I found that seems to explain single stage vs. 2-stage - if anyone cares! I found it interesting.
" Single stage, belt driven units are fine for hobby use. I have had a 5HP/10cfm @ 90psig single stage unit for over 15 years and it is still going strong on regular all-day Sunday use. 'Single stage' does not mean an inferior compressor compared to a 'two stage' unit. The difference is the pressure that you can get out of them. Remember back to your high school science class. When you compress a gas, the temperature rises. In air compression, 100psig is about all you want to do in a single stage because the temperature of the compressed air is at a point that lube oil, aluminum, and gasket materials start to break down. 90psig is fine for most shop uses. If you want higher pressure, you need to cool the air coming out of the first stage cylinder and then run it to the second stage for compression to ~150psig. Again, if you want higher pressure than 150psig, you need to cool that air and run it to a third stage and so on. In industrial compressors, it is not uncommon to have 4, 5, 6 or more stages of compression for really high pressure uses. All need inter-coolers between stages to keep the air temp from melting things to the ground. The first stage cylinder is the largest and determines the cfm rating of the compressor. Subsequent stages are smaller since as the pressure goes up, the volume of the gas is smaller. Multi cylinder single stage compressors will have cylinders all the same size and the piping will be in parallel. Two stage compressors will have a large primary cylinder, a noticeably smaller second stage cylinder and a tell-tale finned cooling tube connecting the two in series. For a given horse power rating a single stage compressor should put out incrementally more air @ 90psig than a two stage since the former uses all the cylinders for the rated volume and the latter only used the first stage cylinder for that and the second cylinder and related horsepower to increase pressure at the expense of less low-pressure volume.
For a quality machine, always look for number stages, not number of cylinders, horse-power, volume @ 90psig, and peak pressure rating. Tank rating is nice to know and the larger the better since a big tank stores more air and reduces the start/stop cycling of a given compressor. If they don't tell you those things, they have something to hide, period. Belt driver and oiled crankcase are features to get for long, trouble free life."
" Single stage, belt driven units are fine for hobby use. I have had a 5HP/10cfm @ 90psig single stage unit for over 15 years and it is still going strong on regular all-day Sunday use. 'Single stage' does not mean an inferior compressor compared to a 'two stage' unit. The difference is the pressure that you can get out of them. Remember back to your high school science class. When you compress a gas, the temperature rises. In air compression, 100psig is about all you want to do in a single stage because the temperature of the compressed air is at a point that lube oil, aluminum, and gasket materials start to break down. 90psig is fine for most shop uses. If you want higher pressure, you need to cool the air coming out of the first stage cylinder and then run it to the second stage for compression to ~150psig. Again, if you want higher pressure than 150psig, you need to cool that air and run it to a third stage and so on. In industrial compressors, it is not uncommon to have 4, 5, 6 or more stages of compression for really high pressure uses. All need inter-coolers between stages to keep the air temp from melting things to the ground. The first stage cylinder is the largest and determines the cfm rating of the compressor. Subsequent stages are smaller since as the pressure goes up, the volume of the gas is smaller. Multi cylinder single stage compressors will have cylinders all the same size and the piping will be in parallel. Two stage compressors will have a large primary cylinder, a noticeably smaller second stage cylinder and a tell-tale finned cooling tube connecting the two in series. For a given horse power rating a single stage compressor should put out incrementally more air @ 90psig than a two stage since the former uses all the cylinders for the rated volume and the latter only used the first stage cylinder for that and the second cylinder and related horsepower to increase pressure at the expense of less low-pressure volume.
For a quality machine, always look for number stages, not number of cylinders, horse-power, volume @ 90psig, and peak pressure rating. Tank rating is nice to know and the larger the better since a big tank stores more air and reduces the start/stop cycling of a given compressor. If they don't tell you those things, they have something to hide, period. Belt driver and oiled crankcase are features to get for long, trouble free life."
