Boy, this stock sprocket thing is confusing. Originally, the Americas came with a 17 and the Speedys a 16. I understand that in 07 they both went to 18. Now, with 09 and later, have they changed again? Is the stock America now back to 17?
I had a 17 originally and changed to an 18. I really like it but sometimes miss the quicker take offs when riding 2-up. I may go back to a 17, but a 16 would be too low for me and I'd always be wanting a 6th gear. On the other end, the 19 would be too high for me. The 18 gears are tall enough.
Obviously, everyone has their own opinion and driving habits.