I'll be the contrarian and say there are are significant differences between 2 strokes and 4 strokes. Two strokes are louder, less fuel efficient, but are ever so slightly easier to maintain. Four strokes are quieter, require slightly more care with maintenance and setup, but are more fuel efficient. Are these differences a problem for a beginner? Absolutely not. So, while I'm being a contrarian, in reality, I agree with Ken and Dave . If you like the idea of a four stroke, go ahead and get one. I think it's a great choice for a plane like a Kadet Senior.

As Ken suggested, buy a tach, it will help you learn how to set the engine appropriately rich, and also help you ensure that you don't underprop it. As for buying Magnum four strokes, I see lots of people reporting positive experiences with them.