^ You haven't heard about fuel compassion?
I'm only posting in regard to wheel size. I've got a People 150 that I've had about two months, and I've put about 300 miles on a set of Heidenau K63 tires, in the stock sizes (80/80-16 and 100/80-16, I believe.) and it rides really nice now. The old tires were five years old, the rear was a little flat in the middle, so I'm not surprised that there's an improvement, but now I can feel the limits of the suspension, chassis, brakes. Not that I generally ride hard enough, but a good set of tires makes it a very road-worthy bike. They're the only ones with the same model in those sizes, from what I can tell. The two Shinko models that have to be paired to get the right sizes have about the same profile from what I can tell, and I've heard from too many people who were riding them that they do make really good tires to not believe it. And the Heidenau tires set me back enough more that I had to think it through, but I have no regrets. Installation is a cost I factored in, and that made the Heidenau tires less unattractive, price-wise.
I've never felt nearly as comfortable on a small diameter-wheeled bike, so the 16" wheels are a must have on a scooter for me.
I'll post a pic of those tires soon.