Well, it's hardly fair to compare golf and cotton balls to this issue. I'd suggest go back and read the parts about how light models can penetrate just fine if they are engine powered. The only time your analogy sort of applies is in the case of lighter and slower gliders with higher than normal amounts of drag. Like the Goldberg Gentle Lady. The design is such that they do not like to fly fast without generating a lot of drag even when ballasted.

Anyhow, there's more to it than just pure weight and momentum such as with the ball throwing analogy. It's about model design, pitch stability trim and maximum flying speed. A slow model can be clean and light so at first it seems like it would not penetrate well. But if it's clean and has extra power that power can go into producing a higher flying speed. So when you look past the golf/cotton analogy a bit further the cotton ball equivalent can do just fine or do even better than the golf ball provided the other features are there to carry the day.