If you take into consideration- landing offsite in unumproved areas, getting into and out of small areas, needing good power for vertical departures in all kinds of conditions (including VERY hot), minimizing effects of rotorwash, good single engine performance, and acceptable speed, no need for fuel endurance over 2 hours- in the rear having good room for patient and med crew, smooth platform that you can even do a good 12 lead with no ghosting, capability for 2 patients if they are not critical trauma, good scene safety with high rotor system, no tail rotor, high mounted engines and rapid start and shutdown-
I would pick the MD900, 902 configuration with PW207E engines. It is also a good hoisting platform.
If you don't need a small machine, don't worry about rotorwash or landing in towns and nasty LZs, and money is not an object- go with a 412 or 139.
Mark