Hi Jeffman,

I have both of these engines and it is pretty much apples and oranges with the exception of one thing. On the Super Tigre .45, the needle valve is on the carburator and you have to be very careful about adjusting it so you don't take the skin off a knuckle. I think it is also slightly heavier, but don't hold me to it. They both run very well and are close in power output. If I had to choose a preference, I think I would go with the OS 46 FX due to the remote needle valve and it is slightly less sensitive to needle valve adjustments. Good luck and don't hesitate to ask questions.

Jeff