I cant really see any disadvantage to the PC-24 except some strips the Kingair may be better suited to. Modern jet, what extra time does it need to prepare and get under way than a similar sized turbo-prop? Once airborne it will be faster en-route and it doesn't suffer the slow downs of commercial traffic if its operating medical priority. If you are comparing two airliners fair enough, but even then these days a 737 can get airborne not much slower than a dash-8 from start of taxi, most of the delay is just securing the cabin. And as said above the jet will have far better weather avoidance and altitude capabilities, as well as better prioritisation when not on medical priority. Pretty sure a medivac from Broken Hill to Sydney or Melbourne would be noticeably faster in the PC-24 than any turboprop. It also gives the opportunity to fly the patient closer to the specialist, or the specialist to the patient faster and in more comfort to get prepared. BTW the PC-24 is designed for these ops, it's not some 40 year old airframe re-jigged for aeromed.
If money was not a consideration I'd get V-22s, huge cabin, lands vertically, same max speed as the B-360, but can deliver the patient direct to the hospital. Might shake them up a bit though.