Having riden dirt bike motorcycles for many years, I've recently seen 4 strokes take over in almost every area. I'm certain they don't make more peak horsepower but they certainly ride differently. The four stroke has more horsepower over a broarder RPM range. It probably doesn't make more peak horsepower but certainly makes more over a longer curve. The same is true with model airplane engines. You are seeing a 4 stroke revolution. Eventually they will take over every part of the market because they are easier to prop, tranistion, do stunts with etc. To visualize the difference picture in your mind to identical airplanes, one with a 4 stroke and one with a 2 stroke, flying vertical at slow RPM, as if in a drag race. Somebody yells GO and both planes take off. The 4 stroke, based on lighter weight, quicker throttle reaction, and broader HP curve would immediately streak into the lead. It would stay ahead for a certain distance and then the 2 stroke would eventually start to overtake the 4 stroke. Who would win the race. Depends: on the length of the race. If given enough time the 2 stroke will make more peak horsepower and take over the 4 stroke. But it will take quite a while. But, if you race to a certain area, slow down for a curve, stunt, or something else, and then speed up again and then do it again, and again, the 2 stroke will never catch up. That's why the 4 strokes are so good at 3D. Up, down, down, up. And there nothing like broad horsepower. It's the feel, not peak horsepower. That said, I still have 2 stroke motorcycles and 4 stroke motorcycles, and 2 stroke airplane engines and 4 stroke airplane engines. But 4 strokes are here to stay and they WILL eventually be proven better in all but a very limited applications. They just simply have to broad of a base to be kept down.
Thanks,
Barry