Benzos are useful for generalized anxiety and especially panic attacks, but practically useless for social anxiety. Social anxiety is pretty much a 24/7 disorder though so if you MUST take a benzo, longer-lasting is better (clonazepam probably being ideal.)
But seek out a different med as well at least, I promise you that benzos are not going to rid you of your SA problems. I know it has "anxiety" in the name but the disorder is so much more than that. Benzos aren't going to do a damn thing for learned avoidance behavior, for example.