Good choice on switching from AT to SW. I have flown both several times and just this week returned from WDW via Airtran. We tried to cut a few corners going the "cheaper" route using AT and definitely paid for it in the long run. First, $60 added for baggage fees (2 bags, round trip), which I knew about beforehand, but considering that they manhandled our luggage so badly that both pieces now need immediate replacing will cost even more. AT employees didn't seem the least bit concerned about my complaint regarding this.
Next, we didn't pay the extra for the reserved seats, so my wife and I were deliberately split up. When we got to the gate the agent gladly fixed it so we could sit together and even acknowledged that the seats to either side of one of us were wide open. This happened on the departure and the return flight, so it seemed quite obvious that the company wanted us to pay extra to "guarantee" that our party might not be split up.
The departing plane seats were the most uncomfortable things I ever sat in and many seats on the plane had disgusting stains and the fabric was torn and in some places completely missing. The flight crew was rude and never even explained why our flight was delayed mid-air for an extra hour.
Plus, AT seats are so small that even a normal sized person would be uncomfortable. I'm 6'1", 190 lbs, so I'm not a huge person, but I literally had less than 2 inches from my knees to the seat in front and had to squeeze my shoulders in for the entire flight.
Southwest doesn't offer guaranteed seating (at least not the last time I could fly with them), but I recall their seats being roomier, more comfortable and since you could choose your seats it was easier to stay with your party when you flew. Plus, their staff was very friendly and made the trip an overall wonderful experience.
