We found the reef life more plentiful off Cozumel, than we did off Roatan. Anthony's Key is a more scenic resort than the Sunscape Sabor in Cozumel, but we had to deal with stairs for pretty much everything at Anthony's Key. There was only one dining facility at the time, up the hill from the beach. Our bungalow (or whatever they called them), was atop the hill, so it was up and down stairs to go eat, to go dive, to go do about everything. That's not a problem for me, but my wife has two artificial hips, and too much stair climbing gets rough on her.
Another advantage Cozumel has is that it's rated as one of the safest travel destinations. Granted, tourism and diving are about the only real "industries" on the island, but with anywhere from 3 to 6 cruise ships in port on most days, it's a multi-million dollar industry for them, and the local authorities seem to be working hard to make sure nothing happens to discourage the tourists from coming there.
We're heading to San Carlos, Sonora, on the Sea of Cortez, in August for a weekend of diving, which is scheduled to dive off the south end of Isla San Pedro Nolasco, where hammerhead sharks are known to gather. We dove off the other end of the island a few years ago, where we got to play with the sea lions. The Sea of Cortez is surprisingly amazing diving, and the abundance and diversity of sea life is incredible.