When comparing equal displacement, you are right, the 2 stoke is more powerful (though not much in it with YS engines), but for what we need, that is not really the issue. All our 3D machines are powered so that they can hover/torque roll at around half power or less, so we want contol at that half throttle, which we get far better with 4strokes compared to two stokes.

With, for example, people here putting Saito 100s on their Funtana 40's, the fact that the saito is less power than say the OS 91FX is not really important.

Ultimately throttle is a fourth control surface, and as with the other three, is very important for 3D flying.