We chose Empress of the Seas because it was a great deal for us. We really enjoyed the service (dining, stateroom, entertainment staff) which was absolutely fantastic and top notch. The evening dining was the highlight of our trip - the server team treated us like regulars and we enjoyed the food like lobster tail, escargot, and steak and fish.
The entertainment staff is small, and the formal programming at night isn't the most highly produced or glamorous, but considering that we enjoyed each night's main show and had a great night.
Cozumel was absolutely beautiful - we did the Dolphin Encounter - highly recommended because you get access to their private beach (beach is amazing, water is clear, however it's not swim-able because it's too rocky, meant for snorkeling other water activities). There is an inlet that is easily to swim and wade in.
We were in an interior stateroom on Deck 9. The interior was cozy and not so tiny. I would advise to get a room in the middle and high up to avoid the most of the waves.