It is hard to know because I don't really know the priorities.
My wife and I have stayed 3 times at Little Cayman Beach Resort (LCBR). We have always gone in the summer. It has pretty good large stuff: big Nassau groupers, southern sting rays, quite a few hawksbill turtles, nurse sharks, eagle rays and nurse sharks. The diving sites at Little Cayman are pretty protected. On top of that, the water clarity tends to be superb. You get great wall diving. You also get very nice reef diving at the top of the wall. LCBR has very good food and decent amenities. If you are thinking night life though, think again. The island has almost no one there. It is about diving, or kayaking, or fishing, or bird watching.
Now, we have both also gone to Virgin Gorda in the British Virgin Islands. The top side amenities are very good there. We stay at Mango Bay Resort. I have done shore diving right there. You can see small stuff. You can also kayak. The diving is in Spanish Town with Dive BVI and they are a very good operator. The Wreck of the Rhone is a tremendous dive. You will probably see quite a bit of good small stuff. However, the area like many is pretty heavily fished so large fish are pretty rare.
I have been to Coco View. It is fun and a good deal. You can dive as much as your little heart desires. But the amenities are pretty basic. However, if you want to do diving, diving and more diving, it is a great place and a lot of fun. The rooms over the water are better than the ocean view rooms (according to my wife, I am not a great judge of this).
Now, I think the diving is better at Utila. I have been to a small resort, Deep Blue which I would recommend. You do two morning boat dives per day. You do either an afternoon boat dive or a night boat dive. Also you can do a shore dive and the house reef is really good. Again, if you are thinking night life, forget it.
For large stuff, you might think of trying one of the Bahama diving resorts. The Bahamas have protected sharks and most of the resorts feature shark dives. I have not been there so I don't know for sure.
Now the Caribbean has pretty good fish and diving. You get the same genera pretty much in the Pacific and the Caribbean. It is just that the better places in the Pacific have far more species of each genus of fish and many of them are far more brightly colored than anything in the Caribbean.