Having done medievac for 5 years around East Africa (although sometime ago) using C-402C and C-404, if I had a choice between the two, I'd take the C-404. If you are the pilot flying it and look after your engines you will find you have a great machine with reasonable performance. 175kts is a safe block speed and with full fuel you have over 1000nm range with reasonable alternates, subject of course to fuel if you divert! :-0
The only weaknesses are:
AVGAS
Pilot induced engine fatigue
Maintenance induced engine fatigue
Weak nose wheel (can be an issue on soft strips)
If you go down this route, please get a decent checkout from someone with experience on the aircraft, not someone looking for a quick sale!!
Turbine options such as the 406 are hard to come by and expensive although the PT-6 is fairly bullet proof :0)
Good luck with it all!
