I've only been to Bonaire, with my wife, of the places you mentioned. We went in May of 2007. I really liked being able to dive on our own schedule, and did a few dives by myself- something I've never done. The reef health and biodiversity was quite nice, but compared to a place like Cozumel, I started to take the reefs a little for granted, mainly due to the fairly similar topography. You swim out to where the wall starts- about 30 feet, which drops to about 70 or 80, and then down to about 140. That said, you can really spend a lot of time underwater if you restrict your depth to 50 or 60 feet. There weren't many compelling reasons to go that deep, other than the wreck, the Helma Hooker. That's in about 90', and worth it. You could do as many dives as you like, so if your by yourself and are into it, you could dive your ass off. We stayed at Captain Don's in a 1 bedroom that was right on the water, with a nice reef right in front. I regret not doing more night dives there, as it was only about a 40 yard swim to the drop off. I'd go again, but maybe with another couple. There are more sites than you could probably be hit in a week, even diving 5x per day.