Does the real reason have more to do with category of aircraft then actual engine type?
Going from a very light piston helicopter doing what may be (not all I know) basic commercial operations (ENG, photo, pipeline patrols, etc...) to a light or intermediate turbine with more demanding operational requirements (precision long line, high altitude mountain landings, night ops outside a city environment, IFR, arctic etc...) may be what the people doing the hiring are considering more so then the ability to push a starter button and watch TOT's rise.
Either way keep building your resume and getting strong letters of reference and you'll be turning down turbine jobs in no time.
Good luck!