ORIGINAL: broke_n_bummin
On lighter planes like profiles and 3D, the extra weight of the 4 stroke is offset by it's ability to swing a large prop.
This is the typical marketing hype mantra.
However it misses the other HALF of what should be added to that statement..
2 strokes, when compared to 4 strokes of equal displacement produce more power.
The "larger prop" really only factors in when you move to a larger four stroke engine.
As it is with equal displacements the difference between the recommended props moving from 2C to 4C varies by only ONE increment if it is not the same.
ORIGINAL: broke_n_bummin
Power wise, the same size 2 stroke is more powerfull, but they weigh more.
Weigh more?
Depends upon which vendor's engines and sizes you are looking at.
Since you have to offset the decreased power of the 4 stroker at the same displacement size, by taking the engine size up several notches... typically the 2 stroke engines end up being about equal or in many cases weighing less... As you get into bigger engines such as the O.S. 1.60 2C, things tend to reverse and indeed a 2.00 four stroker is "lighter" in that range..
e.g. I can put in a .75 2C into my Skybolt, and because the engine is lighter than the recommended 4 stroker with muffler, I would have to add more weight to the nose.
I've flown my Skybolt ARF with both engines, and it is more powerful with the .75, but I prefer the O.S. .91 Four Stroker in the plane for other reasons... And yes I'm swinging a bigger prop, but that is in large part due to the fact that the O.S. .91 is a larger engine.
I do LIKE 4 strokers though and if they were a bit cheaper I might run them exclusively.