It might be, especially if everything was all hooked up to the same lines to minimize air loss and time loss due to switching systems. Time saved would probably be only seconds, my video didnt do the actual speed difference justice, considering the valve was barely opened for the first part of it and I was filling up a fairly large tank (51 cubic inches). Pressurizing the a/c input is still beneficial when charging 200+ psi, doing so will cut the time at least in half. The a/c compressor runs much better if you have the input charged to normal low side pressures than it does just feeding off normal air pressure. I feel perfectly safe in doing so, especially when you consider they are designed to run in such a fashion. Feeding it too much pressure makes mine run too fast, and when the high side reaches 300 psi or so, the compressor stalls out.
