Khalid,
I don't have any experience with that particular design, but I like the simplicity and really only simple tools are needed to construct one.
For low HP (like under 100), piston steam engines are actually more efficient than turbines, in my understanding.
Also add to that the fact that a turbine will require relatively expensive gearing to get the output down to a reasonable rpm.
The actual efficiency depends on a lot of factors; heat differential, condensing/recycling the steam, etc.