I have owned three engines roughly in this size. An OS 40, TT 46 and SK 50 and the TT was by far the easiest to break-in and operate. It started every time by back flipping it off of compression with the throttle set to idle and it is notable quieter than the other two in the air. The fuel economy is also good. I have had zero problems so far with my TT and if I needed another 46, I wouldn't spend the extra money for the OS. Maybe if I had the OS 46 first I would have the opposite opinion but for me the TT came first so that is how it worked out. I would say the TT, on average, is similar in quality to the OS as well. You are always going to find lemons in each brand although some a more likely than others. A YS is more powerful but you typically have to run 20-30% nitro to get that performance and live with the slightly shorter flight times unless you increase the tank size and wet AUW. I like to run 15% nitro so that rules out YS for me in most cases.