That is possibly true, and I think there is research on it, but may indeed be marginal except when dealing with a true oversized racquet.
I'm relying here on an article based on research that swingweight has the strongest correlation with racquet power.
Up until recently the APD had a stiffness of 67 so that's not too excessive, but with stiffness its a question of how much stiffer makes a big difference.
Nearly all modern racquets are on the stiff side.
I forgot they changed the stiffness of the APD. It was at 67, which I believe the K90 was.. 66 or 67 as well.
But your mistaken again because the apd and the k90 does not have the same swing weight.
If they both had the SAME swing weight (which they don't) then the apd would be more powerful because it is stiffer. But since it doesn't it is not. Understand?
le sigh...
We were specifically discussing in the event that ALL things were equal, IE swing speed, mass, swingweight, the APD is marginally more powerful because of its larger headsize (more string to work with), and slightly higher stiffness.
Now, you're claming the K90 is more powerful because in stock form it has a higher swingweight. This would be true IF the swing speed was the same on both frames, but many people find they can swing the APD faster because it's lighter, and so are able to produce more power.
I don't know about you, but I generally feel that when I encounter an APD/PD, I tend to see more pace and spin, but it's not nearly as heavy of a ball. The old mids may not produce the same mph in most people's hands, but the shot is heavier for some reason.
Personal experience, again. But I would rather play against an APD user who tried to spin me off the court, because his shots aren't as tough to handle nor as precise as an experienced mid user.