carsickpuppy ,
What kinda op are you getting into ?? mountain , logging , island hopping or in PNG ??
If I were to compare a 139 with a Mi-17 variant ... at sea level or thereabouts I'd pick the 139 .... but anywhere above 8000 ft I'd say no one beats a Mi-17 / Mi-171/ Mi-172 kind of chopper .
Its a rugged machine , one can really throw it around and it performs .You 'd ofcourse need enough spares to keep em flying . They'd work great at the poles too ..Ask the Yanks why they chose them ??!!