I've got the big one. It fits in the overhead if you put a pillow under it to raise the medal handle high enough to let the door close. (Yes, SWA still has pillows!!!) You have load the bag upside down (wheels up) on some planes (I think some -300s) to make it fit. Sometimes the Flight attendants just make me put it in sidways so they won't have a problem during general boarding. (We preboard as jumpseaters and have all the overhead space we want).
If you have the wider bag, like me, your pockets will get scuffed in the cockpit. I don't put anything in them. Also, the longer bag catches on a piece of metal and you have to lift the bag up off the floor to get it all the way under the second jumpseat. If I didn't have a PNS bag, I would be damaging the bag with that piece of metal poking up. But my bag appears to be holding up.
In short, it will work but many will tell you its too big and will advise you to get the smaller one. But no one gives me any grief about it.
