Roatan was my favorite, by far. Paid extra for the Dolphin Experience at Anthony's Key Resort and it was AMAZING!!! Swam with the babies, got to pet them and even touched their little teeth. I'm a dolphin fanatic, so it was heaven. After that, we went to a beach that was awesome.
In Cozumel, we took the speed boat excursion which was an adrenaline rush. They speed you along and then do crazy 360 degree turns. We arrived at a private island where we had free (well, technically we paid for all of it), food, floats, kayaks and beach chairs.
In both Roatan and Cozumel, the water was crystal clear. Beautiful places!!!