Photog has done a great job of hitting on the different sub-catagory of scooters. I went with a Yamaha Zuma which is a 50cc 2-stroke. I've posted ad naseum about my driveline tuning which probably makes it sound like all I do is tinker with the thing. The reality is that it is very easy to work on and my tinkering doesn't preclude actual riding. I live in a hilly area and choosing a 2-stroke probably wasn't the best call. But I love 2-strokes and that was that. So I'm still tinkering toward perfection but in all honesty if it never got anymore "perfect" I'd still be happy with the scooter. I've had so much fun!
My buddy bought a Vespa ET4 at the same time I bought my Zuma and if I'd known how much I would enjoy scootering I would have spent the extra money on one. While getting max performance out of small displacement is nearly an obsession for me there is something to be said for purchasing an easier path to ones goals.