I've got an OS 46ax on my mustang, that engine really hauls it along nicely. After 1 season on the engine, about a gallon and a half thru it, it tachs about 13,500 on a MA 11x6 on a nice cool day.

I broke in a Supertigre G45 for a friend last week, and I must say I'm impressed with it initially. I did find that the recommended 3 turns out on the HS needle was too rich to start it (try 2 turns or so), but once fired, it ran very well. On the same prop as the OS, by the end of the tank it was easily holding 13100, and it's not leaned out yet. Throttling response was adequate for a richly tuned engine, time will tell on this one, but my initial impression was very positive.

The OS has a nicer looking muffler, tho I've popped the thru-bolt on it a couple times now. If it's even slightly over-torqued, thermal expansion of the muffler pops the bolt. I'm out a baffle now (lost in flight), but all that did was gain me a couple hundred more rpm. Without the baffle, the engine acts like it's on a mild tuned pipe, really turning up in the air. Even after loosing half the muffler in flight, the engine performed flawlessly. This one has never deadsticked (knock on wood....)

The ST muffler is UGLY. It won't pop a thru-bolt, tho, as it's crimped together.

I've worked with numerous evolutions, the Trainer P(o)S, and the non-trainer .46. I find the trainer power system idle needle to be too sensitive, and too easy to turn (doesn't always keep a setting... This can be fixed easily enough, tho.). Idle mixture is key to good running in an evo, completely intolerant of mis-adjustment here.

The Evo's have an interesting styling with the upsweapt fins.

The only Magnum I ever owned was old, second hand and I didn't like it much. I won't weigh in on that one, I know they're popular with many and they're better to comment on them.

For my money, I'd go Supertigre, if OS was out of my price range.