In 3000hrs of Robinson flying I've had 1 stuck valve(R22), & 3 x magneto failures(R44). About the same turbine with no failures - Speaks for itself.
I'm no mathematician, but your experiences may not be statistically significant.i.e. 4 in 3000 (0.13pc) might not be any different from 0.0pc, statistically speaking.
Ive got 7000 hours on turbines and had to shut 1 down. Does that make it better or worse than the zero failures in 1000 piston hours?
D