737 is a very shoulder to shoulder like experience, the rule is you are generally more comfortable with your neighbours in a 737 vs a A320. Especially toward the rear. I always feel like I am squeezing myself to fit in any way I move around whether entering, seated, bathroom. Flight Deck isn't much better, A320 you can even mod Airbus for 2 Jumpseats, 737 feels like it can barely cope with the one.