I think what Theta cutie meant was that Theta was one of the more "well known" sororities nationally, as opposed to being exclusive. Most people in the greek system know a lot about the other GLO's, but people outside of it are more likely to have heard of KKG, Theta, Tri-Delt, or DZ as opposed to say, Alpha Sigma Alpha or Sigma Delta Tau. And it has nothing to do with the quality, because all 26 orgs in the NPC are equally awesome. It's just that some are larger and have more chapters, and therefore are more well known. And maybe that's why outsiders PERCEIVE these groups as being more "exclusive." Anyone in the Greek system should know that all chapters are different, and that nationally all groups are great, and no one org is more exclusive than another when it all gets averaged out.
Anyway, Bubbles, best of luck in your rush -- I hope you get Theta if that's your favorite but I'm sure you'll be just as happy no matter where you go.