Help me choose

A couple of things that I want to offer. PLEASE check the duty cycle for the unit. No matter the size of the tank, you don't want the motor and pump running too long at a time. If at all possible get a cast iron pump or at least iron cylinders. Check the speed of the motor. If I remember right the speed for a good quality motor is about 1700-1800 RPM. Spend the extra and get an automatic tank drain. We got to the point we would figure one in as part of the unit. Never had a customer complain about not having to worry or trying to remember to drain the tank.