I have been to Cozumel many a times and this year I went to Bonaire with my wife. The diving in Bonaire was SSSSSSSSOOOO EASY it made me weep with joy! Right from shore - rent a truck and drive to the dive destination of your choice, at the time you want, at the pace you want...and for less than you would if you were boat diving in Cozumel. We paid about $400.00 for the brand new truck rental and unlimited tanks for a whole week!!!!!!! That's cheaper than Cozumel.
Bonaire drawbacks:
1. It has the nightlife of an assisted living home.
2. It is a desert and unless your really into donkeys, goats and lizards there ain't much else to see on the island except that which is underwater.
3. I found the night diving to be a bit meager-not like Cozumel with all the huge lobster and crab and in general there are not as many bigger animals in Bonaire as in Cozumel. Though I did see a turtle and bat-nosed ray(I think that's what it was, it moved through the water like a bullet) right while diving right off the hotel dock.
4. Dining out is expensive.
5. It takes a long time to get there from Minnesota-and according to classical physics about the same time to get back. However, this copious air time provided me ample opportunity to figure out my Cobra dive computer and read how to take underwater photographs-though judging by the quality of the photos many will say some additional air/study time would have done me good!
Would I go back again?
Not for a long time......there is Australia, Monterey CA. North Carolina, Mexico's cenotes, Galopagos, Red Sea, Alaska, Sea of Cortez, Ginnie Springs, ......too many other places to dive in the world. But I love Boniare and have many photos to last me until I return.....someday.