About inverter models, ask around for the cost of maintenance. When I was shopping for my aircon last year I asked for maintenance cost and inverter models cost double for maintenance! (RM200 for normal one vs RM400 for inverter/O2 models). Not sure why, but one of the reason is that they used environmentally friendly gas (just like the car aircon switch to R141A many years ago, at first they cost a bomb!).