Thank you all very much for the useful real world info. Sounds like fuel burn numbers between the LR45 and LR60 are fairly similar which is one of the most important factors for us and the reason for not moving the G4 on shorter missions. The LR31 cabin size and lavatory would be an issue...so we've narrowed our search to the 45 and 60.
Are all the LR 60 APU's Electricity only? Or do they have options for an APU with AIR as well??? If not, the LR45 is sounding better and better since we do operate out of warm climates most of the time.
Thanks again for all of your replies!