ok, its like this
free turbine is sort of like the automatic automobiletransmission of the world
fixed shaft turbine is like manual transmission
fixed shaft is more responsive and a tiny bit more efficient
free turbine is a bit simpler
I have about one hour of free turbine time (king air)
I have thousands of hours of fixed shaft turbine.
I'll take the fixed shaft anyday. however one has to remember to shut the engines down correctly or a minor problemhappens with starting