Projectors produced before 1973, cannot play sound. Because these are older, they are also typically harder to find and more expensive.
Most, but not all projectors made since 1973 will play sound. Sound projectors are much more common and cheaper than silent models.
Although the film width is the same, Super 8 is categorically different from standard 8, and a projector that works for one may not work for the other. The most common types of projector available today are duals that can play not only standard and Super 8, but 16mm as well.
Because Kodak did not use its patent on the Super 8 system to limit projector production, the quality of projectors varies by brand as much as by age or use.
Although Kodak's projectors vary in quality, those made by Bell and Howell are considered some of the best, because in spite of Super 8's popularity, they still treated the medium with the prestige of standard 8. All Bell and Howell Super 8 projectors have model numbers starting in the 400s; however, some lower 400s are standard 8.
Elmo and Eumig projectors have also held up well over the years--they are gentle on film and have well-built lenses, good sound and lots of features.