I wouldn't get hung up on the ringed engine lasting longer. My original OS FX engines are going on 6 years and still run like new. Personally as an instructor I have found that Thunder Tiger Pro engines are about the best value out there. OS engines are user friendly and have more power but they also cost about $20.00 more. Maybe its because of our altitude at our field but for me, Super Tiger engines are too miserable to try to get to run right. I bought a Tower 75 engine to try it. It runs well with tons of power and I am very happy with it. A lot of the TH 46 engines don't want to stop when you close the throttle, possibly due to an air leak somewhere. TH has been good at replacing the engine if you get one of these but if this would bother you then I would look at the TT engines. If the extra $20.00 isn't an issue then I would get an OS 46AX. Its the newer version of the FX and its a terrific all around engine! [8D]