If prices are similar, I would go with Airtran only because you can get seat assignments prior boarding. I love Southwest for their prices (out of BWI), but now that they are in Phila, competitors like US Air ansd Airtran have dropped their prices. With Southwest, we would get to the airport extra early and have one of the first set of boarding passes and still end up sitting towards the back of the plane because familes ith small children get to board first, regardless of boarding pass #. Well, you can imagine that any flight to Orlando is mostly filled with kids.