I have been to Cozumel a couple of times before the last hurricanes and the diving was excellent. However, I found the atolls off Belize to be far superior to the diving in Cozumel.
The atolls off Belize have the healthiest, most colourful reef I have EVER seen. The sea life was abundant and we saw many large and small critters. There were tonnes of sea turtles, eels, nurse sharks, eagle rays, sting rays, etc.
What I have heard from people who have been diving in Cozumel after the last hurricanes has not been favourable at all and they were disappointed compared to before the hurricanes. They also did Belize more recently than me, and found it to be absolutely awesome.