just a guess, but in omaha, I would bet that it is a straight, because on the flop alone, usually at least one person flops 2 pair, and usually others flop a flush (or flush draw), or a straight(or straight draw), and end up making on the turn or river. I don't see 2 pair hold up a lot unless it's a short handed game, so I would be it is better than that, but in Hold 'em, I am not surprised when 2 pair being "an average winning hand" because depending on what the cards are, a lot of times when one makes two pair using each of their hole cards to make it, they probably think they have the best hand.