Thunder Tiger 46 because of great idle, transition, has great horsepower, great price, topend, reliable, and last forever. I have the OS FX 46 and Thunder Tiger 46Pro and the Thunder Tiger has the edge. However, a Tower Hobbies muffler is needed to wake both engines up. If you don't want to caugh up the $15 or so at least remove the muffler baffle and don't forget to Locktite the heck out of the screw and nut that runs through the muffler and screws that go through engine.