So what kind of vespa should you get? It all depends on what you're looking for. Let's go through a couple popular models, starting with the earliest:
The G.S.: Also known as the Gran Sport. Made from 1955-1961. The G.S. is a landmark in the vespa family for its supple curves that blend so well to create a whole. A total work of art. It is much sought after, a great scooter if you're not too interested in using it day to day but rather enjoy it as a collector's item as it is spendy to maintain with parts that are pretty rare. While the GS is hands down the sleekest and most appealing of the vespa family, it is an absolute bitch to maintain. The thing always breaks down, it's just something that goes with owning one.
The S.S. 180: The Super Sport. 1964 to 1968. The Sequel to the G.S. and the prequel to the Rally family, the S.S. 180 sports a trapezoidal headlight that gives it a quirky kind of look. Very popular in its time during the 60's and coveted for its mod status, making it a little more spendy then you would have expected. But it is fast and can easily keep up in traffic, topping around 60mph. Problems with the S.S. include poor 6 volt lighting and on early models, a distressing tendency to seize when not jetted correctly, or as I like to call it- skidding all over the road because the engine just died and the back wheel is locked up because you forgot to pull the clutch in. Seizes can range from soft- simply killing the engine, or hard- the piston welds itself to the housing case. This is usually corrected by replacing the engine with a P200 engine.
The Rally Family: The Rally, the G.L. (Gran Luxe), the Sprint, the Sprint Veloce, and the S.L. (Super Luxe). These all basically look a lot alike. In this family things start to become a bit cheaper, and easier to maintain due to parts readily available. Out of all of these, the Rally is the most popular. The Rally 200 basically has it all: a spare tire underneath the left cowl, glovebox behind the leg shield, fuel injection (so no messy mixing by hand) and the largest tank out of all its relatives. It is fast with a speed of up to 65mph, reliable, and although the later models started to become more "boxy", it's still considered somewhat sleek. Other models within this family are fairly identical with the Rally. Differences may occur in tire size, the size or c.c. of the engine, tank size, the fuel injection, and the port system within the engine.
The VBB/VBA: The VBA/VBB Vespas are so-called after the prefixes of their VIN numbers. These numbers are found on the left side of the scooter frame, underneath the cowl where the engine sits and are used for identification of type and year. The VBB/VBA's are the only ones I hear called after their vin names most often, rarely will you hear a Rally called a VLB, unless you're ordering parts. The Vespa 150 is a robust scooter and capable of use on today's roads. It suffers from poor acceleration, especially on three speed models, but can reach 50 mph... eventually. Kinda scary in my opinion. The 125's are a bit too slow to keep up with traffic. Acceleration and top speed limit them to side streets and slow roads only. Poor 6 volt lighting hampers all in the range. Furthermore, the 8" tires employed on all of these scooters makes them less than stable, and hitting a pothole at any speed can be a major problem. Still, people love them for their shape and curves and tend to upgrade the tires, forks, and engine.
The Smallframes: These guys are tiny and were initially intended for women who couldn't handle the largeframes. Smallframe Vespas are so-called because their body design is much narrower than all of the other Vespas. They do not have removable cowls (sidepanels) and instead have these small removable "doors" thus causing working on the engine to be a nightmare. I've been told it's like working on a watch, where it becomes very difficult to work on the carb or fuel line and impossible to get to the clutch unless you "drop the engine", pulling it down from the chassis. But they are generally lighter and more maneuverable than their bigger counterparts. The original smallframe design was for a 50cc scooter, and eventually Piaggio shoehorned bigger motors into the cramped chassis. The largest capacity smallframe was the 125cc Primavera. The 50cc Vespa is laughably slow and should be avoided at all costs. The 90 and 100cc models are slightly faster, but are still far too slow to be safely driven on today's roads, you're going to want the extra c.c.'s in dangerous situations. The 125 Primavera on the other hand, is very quick and is most certainly capable of holding its own. All around, it is one of the best designed Vespas. It's considered to be the best handling Vespa. In addition, all of the smallframe Vespas can be easily modified for increased performance. When tuned properly, a smallframe will easily smoke just about every other scooter on the road in terms of both acceleration and handling. Problem areas include 6 volt lights for the whole range (except the 100 Sport), and incredibly dodgy wiring for 70's models with turn signals. (especially on 1974 models)
The P200: Last but not least. The P200 is considered to be the workhorse of the vespa family for its durability as a great daily rider. With the P200 it's all about what's more important: looks, or durability? Made in the 80's the P200 is extremely boxy compared to its ancestors, but what it lacks in looks it makes up in engine. Because of this, people will usually replace older largeframe model engines with the a p200 engine. This cannot be done with smallframes. It was the best engine made sofar in the vespa family and last of the 2-stroke engine in the line. 5 port engine, fuel injection, 200c.c., basically all around strong, I've heard of people driving from Washington to California and back with no problems. The only problem I have with it is, being that I'm female, 5'6", I have difficulty with it being very tall, much larger than the earlier models, and heavy which may make it difficult for shorter folk to control, something you'll need when you're out in the rain. Still a great scooter, parts are extremely cheap, one of the last all metal bodies.