I think flightinfo.com might get you some more responses regarding World, Southern, and Omni.
And I think you are correct in that all 3 are hiring. I know World became a bit "choosey" after the Chapter 7 of Gemini and only hired guys with MD-11 ratings for a while. Hopefully that supply of dudes is close to exhausted, and you'd have a shot at an interview. Out of the 3 companies you mentioned, I'd say most of us would agree World is definitely the best one. I have a bunch of ex-ATA friends at World, and the last I talked to them, they all really liked the outfit.