I've had both a scooter and 700cc Honda shadow for about eighteen years. I ride the scooter much more often because of its convenience.
It's true that the smaller the engine, the better the gas mileage. But with a small engine you get lower top speeds. Even if the roads that you travel have a speed limit of 45mph, there are times when you have to accelerate to 60mph. There are also hills that have to be climbed.
A 50cc moped won't do more than 35mph. A 150 cc might do about 55-60mph(60-80mpg). I'm running a 250cc Honda Elite (1989) with 15,000 miles on it and I get 70mph and 70mpg. That's an honest level road, no wind figure and day in and out gas mileages. My Honda 700cc shadow gets 49mpg.
At 250 pounds and auto xmission my scooter is very convenient as a fair weather machine. Come winter with snow and ice on the roads, you won't see scooters or motorcycles.
I have to disagree vigorously with Chili's big scooter. In my opinion it has all the disadvantages of a full motorcycle (size and weight) and the disadvantages of a scooter (small wheels). The salesman won't tell you, but you can expect only 4-6 thousand miles on the rear tire of a scooter and 8-10 thousand on the front tire. That's because of the small circumference of the tire.
On my previous machine, also a 250cc Honda scooter, I got 43 thousand miles before a major xmission failure made me junk it.
In Pennsylvania, a scooter is considered a motorcycle and the driver must take a test and get an endorsement on his license. However there is a a no-test learners permit available for one year duration. In this state you need an annual inspection, insurance and must wear eye protection. Helmets are not required for motorcycles.
I've had my scooter on the interstate lots of times but it's a bit hairy due to the light weight and passing heavy trucks. I'd much rather use my heavier motorcycle then.
I was at my Honda dealer today and they are completely sold out of scooters with people waiting in lline.
As far as the brand, you have to approach it like an auto purchase. Who will repair it? Where do you get parts or tires? My suggestion is to browse the usenet group alt.scooter for comments from users. If you don't have a usenet reader, you can go to google groups for info.
I have to disagree with the guys bad mouthing tiny wheel performance. I have no problems with it at all. Frankly it's a bit more difficult transitioning from a scooter to a motorcycle than from a motorcycle to a scooter. Because of its low center of gravity, a scooter is a lot easier to learn than a bicycle. But you do have to watch out for the deeper and bigger pot holes with your smaller wheels.
I still get laughs from the cage (auto) drivers when I park my scooter. But they stop laughing when I say "70 miles per gallon".