I love cruising, and I totally get you on the tiny bathroom. I am mildly claustrophobic so I just leave the door from the bathroom to the cabin open (I went with my husband twice and my son once, neither cared).  One thing I noticed- Carnival is cheaper, so they tend to have a higher weight medium. Princess is mostly older guests, so less "fit" people but still human sized. The longer cruises tend to have less fats, and by the first day at sea they are all congregated by the food courts anyway. And cruise ship gyms is a shitlord paradise.