I posted on your thread at the "other" board, but forgot to add why I like the onboard compressor with a tank.
My system has a slow leak. For the life of me, I cannot find it. I have sprayed soapy water on all the fittings and can find NOTHING! That means I would go through a lot of CO-2.
Also, with an air sys. (vs CO-2) all I do is flip the switch and I am ready to go. No stopping and turning on a valve. Some people do not have a valve, but for the above mentioned resons, I would think they are a good idea.
BTW, check MPS