I did the 15 tooth. Really like the improvement. First gear matters again. Feels much better in 3rd and 4th gear. 5-6 gear are still screaming between 60-75mph. But that's how this bike and 300cc's works. I get it. I didn't buy it for the interstate.
Standard chain and sun sprocket were installed. I wear a helmet, so I haven't heard the non dampened difference. Sprocket change makes me compelled to keep it. It flicks like a champ and feels nimble enough for my riding style.
Really appreciate everyone's efforts and input,