Two stroke versus four stroke truly is a matter of preference. I currently have 4 flyable planes and 3 have four strokes. I have a kit in progress that will get a four stroke. My brother currently has 5 or 6 flyable, all with four strokes.

My main reason to use four strokes is that they seem to run better than two strokes at low throttle settings. This could just be my imagination, but I think it's really true.

I also like the sound of a four stroke better than the sound of a two stroke.

Four strokes have more moving parts, but my brother and I have not had any problems with our engines. You need a tach to set the needles, and they tend to stay set. Otherwise it's just fuel up and go.