Hmm, interesting argument. Yes, car AC systems run at much lower pressures compared to home AC systems. What do you mean by "I doubt efficiency concerns with MVAC are comparable to those for comfort cooling."? I think that efficiency of a car AC is very important also. The car companies are very concerned about gas mileage, and the longer the compressor runs and the more force it takes to turn it while it is running, the worse the gas mileage will be. Also, why would lower pressures be more important for a car AC than a home AC?