I hate Owens as a person, but I'd have to go with him.
Chad Johnson is obnoxious and as big a media whore as I've ever seen. And he's not as talented as either Moss or Owens.
Randy Moss is the most physically gifted receiver in NFL history, but he's never had the drive to be the best. Last year he didn't even look like he wanted to be in the league anymore. I don't know what he would bring to the table, if he would bring anything at all.
And Plaxico has always been somewhat overrated in my book. He played lights out in an NFC title game, and then caught a game winner in the Super Bowl, and suddenly he was being propped up as being elite. I'd also have concerns about his ankle, since he was having issues with missing practice regularly prior to shooting himself in the leg. At 34, with two years away from the game, and without being dominant before the injury, I don't know if he'd bring much to the team as well - especially with an abbreviated off season.