Christine,
I think the biggest benefit most would agree a string suppressor offers first and foremost is noise suppression. It changes the pitch of the bow's shot from a "twang" to a dull thud.
Other benefits include being able to pick up a couple fps, usually. This is accomplished a couple ways: One, the shooter can usually remove any leeches or Hush Kit items on their bow string, which affords a gain. Two, some people have stated an increased gain in speed because the suppressor stops the string at brace, offering a "cleaner" release of the nock. Those who argue this state that the string will actually "pull" at the nock almost imperceptibly as the string goes past brace and the arrow attempts to free itself of the string.
Of course, yet one more benefit is not having to worry with "arm slap" as much, both on low-brace height bows, and in colder temps when the shooter is bundled up more.
Hope that helps! And hope to see you in a couple months at the Illinois Deer & Turkey Expo again!
