I have a Tower Kaos and several .46-size engines.
OS .46AX: Easiest to run. Powerful. Very reliable. I have these in 2 twins.
Thunder Tiger .46 Pro: Takes more time to break-in. Runs good. Somehow, I never took to them.
GMS .47: Takes a while to break-in. Can stop at idle before break-in is complete. Once they smooth out, they run great. I have 2 in a twin.
Magnum .52XLS: Most powerful of the bunch. Can be tricky to tune, especially for idle mixture. I have 2 in a twin.
Evo .46: Easy to start & run. I never actually put it on a tach, but I felt it was down on power compared to the OS, Magnum & GMS.