Funny. I know my suitcase will always fit the right way in a 737 bin (front upwards, top handle facing the aisle) ... but on an A321 I almost always have to lay the handle to the right, wheels left, taking up unnecessary horizontal space, because the upper part of the bin isn't deep enough to close given top thickness of the suitcase - even though it looks like it fits in the lower lip before you try to close it. So these days if I see I'm getting on an Airbus, I have to try to get in early and grab the extra bin space. Whereas if it's a Boeing I'll usually be at the bar until 2 minutes before they close the gate..