We've flown both.....SWA more than AT and yes, AT is notorious about changing their schedule.....however, it really depends upon which airport you're flying from/to.......we've flown them from ABE (Lehigh Valley, PA) and since they only have one flight per day in/out of there.....it's pretty tough for them to change the schedule. However, in/out of PHL is another story. They also charge for bags and assigned seating......one way around the charge for assigned seating is to enter the AT site from Kayak.com and for some reason, there is no charge to choose seats by using this workaround. I also seem to think there is less seat space/leg room on AT than on SWA......however, that may depend on the equipment AT uses for different routes. With SWA, you know it's going to be a 737......six seats across......since that's all they fly. All in all, I think it comes down to pricing and convenience of flight times. Personally, we prefer SWA, but, we can only get them out of PHL ......so it means a further drive to/from the airport for us and also, it seems like every flight back into PHL is delayed .......sometimes for a short period of time....sometimes for hours.......which is not a SWA problem, but, a PHL airport problem.....no matter which airline you're flying. Other posters have mentioned the "cattle call" boarding of SWA........I don't look at it that way at all......I prefer to think of it as "choosing where I choose to sit as I board the flight" which can mean different things for different trips. When traveling with our adult children and grandson......we don't mind sitting around families with small children. However, when it's just my DH and I.......sometimes we prefer to choose NOT to sit near a lot of little children.....on SWA we CAN do that......on AT since our seats are already chosen.....we have no control over that.