I would say the big difference between Curacao and Cozumel is shore diving vs. boat diving. Generally, more shore diving should also mean more opportunities for snorkeling, I would think, and at a more reasonable cost since you don't have to pay for a boat every time you want to go out. Curacao doesn't have the number of large fish, but it has plenty of juveniles and they tend to hang around in shallow areas, so snorkeling should be great from that perspective.
For snorkeling, I recommend going to the Tugboat, Cas Abou and Porto Mari (among others) and if you get all the way to the Western end of the island, Playa Kalki.
I am sure there are lots more places, but I don't snorkel on the island so will have to defer to others who do for more suggestions.
I don't know anything about the gambling or golf. Diving, and I assume snorkeling is similar between Curacao and Bonaire, I am not sure I would spend the time and money to do both, especially since Bonaire is VERY dive-centered with not much else to do.