As was mentioned in a similar thread about the EC-135 not too long ago (see
http://www.pprune.org/forums/showthr...ighlight=ec135), the ADAC Luftrettung GmbH in Germany has a mixed fleet of EC-135Ts and EC-135Ps.
Maybe they or possibly Air Lloyd Luftfahrt Technik GmbH, who do most of the maintenance work for the ADAC helicopters, could give you some comparison information on what the pros and cons of the two different engine types are.