I think the question should be more like "what is the best engine for the type of flying your going to do on a certain plane?" My favorite sport engine is a G90. I have one of them in a Shoestring and I don't believe i can get better performance from any other engine. I also have some Jetts for which I would not waste in a Shoestring .

Then I have planes that a G90 would not bring out the best in that a Jett would.