Would like some insight into an upcoming purchase. Trying to decide between three electric compressors, specs below: 1. 8 gallon tank 2 HP 125 PSI- Air delivery: 4.5 CFM @ 90 PSI, 5.5 CFM @ 40 PSI 2. 10 gallon tank 2.5 HP 125 PSI- Air delivery: 5.3 CFM @ 90 PSI, 6.2 CFM @ 40 PSI 3. 21 gallon tank 2.5 HP 125 PSI- Air delivery: 4.7 CFM @ 90 PSI, 5.8 CFM @ 40 PSI #2 is about $30 more than #1, #3 is about $70 more than #1 All three are oil lubed. I will be using it for DIY on the house, car and tractor, infrequent use, but perhaps heavy use when I need it. I will need to use an extension cord 99% of the time. I have an old house that requires lots of rehab, and its my first go around with this type of large project, so I can't yet say everything that I will need it for. I'm leaning toward #2, but don't know what I'm missing, like what does the larger tank of #3 get you?