From MopedWiki

Overview

The Vespa Si is the sportiest model Piaggio sold in the United States. The cantilever suspension and bulky forks make the ride very durable, stable, and comfortable, making this moped a great candidate for speed.

Comparison

The Si is lighter and more compact than the Vespa Grande. It has 4 spoke mags that are tougher than the spoke wheels found on most other mopeds. It also comes stock with a variator, giving a better acceleration than its single speed brother, the Vespa Ciao. The Si's engine is no different than any other Vespa moped motor. It comes with a Dellorto 12:10 carburetor.

Specifics

The Si comes with parts that are not common to any other bikes. The 4 spoke mags are very desirable and are can also be found on other versions of Vespa mopeds only in Europe (Ciao-Mix, Bravo-Mix, etc). Also, the taillight and headlight are specific to the Si, meaning replacements will probably have to be sourced from Italy. As goes for most mopeds, the sidecovers with the "Si" logo are hard to find when lost. There is also a shroud underneath the gas tank which holds the wiring harness and horn.