Okay, I'll put in my $.02.
If I want throttle response but power isn't the biggest issue I go with a 4 stroke. If the throttle response isn't critical I prefer the 2 stroke. 3d type maneuvering is the primary time I want really crisp throttle response. My biggest headache with a 4 stroker is I can't hear it running. I want to hear my engine all the time I'm flying. I have a Saito 91 in a GP Super Sportster and it's the sweetest flying plane but I can never hear the thing. I grew up hearing these things scream and it just doesn't seem right being so quiet.
Later,,,basmmntdweller