I don't have a size requirement, but I immensely dislike postage stamp rooms. I just had an attic-closet at Ett Hem (avoid room 8!). And just prior to that, I had a room at the MO Barcelona that was much too small. I had to move furniture to get to the mini-bar. Can't image returning to either of'em. And my only stay at the Montage Beverly Hills was in a room that would give a goldfish claustrophobia.

.....ing aside, I prefer two separate rooms even when I'm traveling alone. This is normally called a 'suite' here.