I've dove with Aldora twice (this last time for 10 days in November) and they ALWAYS analyzed my nitrox tanks with me watching. Every single time! For 24 dives for the November trip. And yes, normally they were right on time, but a couple of times they were somewhat late, and one time, it was an hour late. Things happen. When I dove with Dressel, routinely, especially the last year, boat times NEVER were on time. And now it's much worse after the huricane ruined the dock and they can only load from one side of the dock.
I've dove in Dahab in the Red Sea, 4 places in Bali, lots of dive sites in Koh Tao and Koh Phangan, Raja Ampat, and Belize, and none of those places have better visibility than Cozumel-NO ONE! Yes, Raja was amazing-but the visibility was never as good as Cozumel's and sometimes it was pretty dismal.
I've come to Cozumel six times. I keep coming back here. Why? Because it's great! It's fairly close, the visibility is awesome, I love the swimthrus (I've never seen better swimthrus anywhere), there are a wide variety of sites, I love San Miguel, I can go across to Playa Del Carmen and dive cenotes, I've seen a hammerhead here twice ( and I haven't seen one anywhere else), and now I've even seen seahorses here, there is nothing like seeing eagle rays or seven foot green moray eels swimming near you, I love seeing toadfish, and there is nothing like the excitement of a great drift dive! I could keep going. There are wonderful, wonderful restaurants here. The people in the town are lovely to talk to. The National Park is great if I can ever pull myself away from diving for a day. I could dive Cedral Wall and Palancar Caves just about every day. If I am being critical-the port getting closed with bad weather, that's a bummer, but stuff happens. The park fees going up-well, all prices for everything are going up. I think there are some wonderful divemasters here-people who love their job, and love taking people out for great dives. You don't always get that. You certainly have lots of dive shops to choose from here. I would rank Cozumel as either 1 or 2 as the top destinations I have been to. And I imagine I will keep coming back as long as I can dive. In fact, I am booked for 2 weeks in October. the biggest problem I have with Cozumel is not Cozumel itself, but the difficulty I have to fly there from my local airport as I can't fly nonstop, and usually the connection is under an hou, and I won't book that. and coming back is worse as I won't book with less than at least 2 1/2 hours to clear customs (Miami you need at least 3 even with Global entry), and it becomes very, very difficult. I can't compare it to anything else in the Caribbean other than Belize as that is the only other place I dove. The visibility wasn't that great there.