Buy what you wish, and can afford, not necessarily what others are using. I'm sure each one has pleased the owner, therefore the above recommendations. I have several O.S. 91 FS and several Magnums. I forget which is in what model. Unless I look at the log books, I really can't say what engine it is that I am flying. Have had each for over 5 yrs. with no problems. Just follow the mfrs. instructions on break-in and fuel....Cheers!!