BP
The impression that the Koala descends faster than the others is not proven and rotor inertia is no worst than eg Gazelle. Having completed many full EOL's the only comment I have is that leveling the skids for the run on, because of the rotor mast angle takes some practice.
As for the range and fuel consumption;-
With the 3 tank configuration, full fuel and full POB(8) gives 2.5 hours with reserves. With the 5 tanks fitted full fuel and 3 POB with luggage will give 3.7 hours at 125 kts (68%TQ) ISA. You tell me another heli with this range/load. Get up to 5000PA and the range is even better. These are proven figures with the Mk1 tail rotor, what differnces there are with the Mk2 tail rotor I do not know. Mk2 T/R is very much quieter than the Mk1.