One of the things that seems to recur on this and other threads is the number of posters who list diving with 3, 4 or even more ops on Cayman that they dive with. This suggests to me that they might not have been happy with the original company and are shopping around, or they booked late when boats were full. My own philosophy is that once I find a good operator, I stick to them exclusively...
That's true for a lot of places but it hasn't worked that way for Grand Cayman - at least not for us. In many destinations, we book a combined package for lodgings and diving and exclusively use the dive op associated with the resort. On Grand Cayman we stay in an apartment or condo, enjoy a lot of topside activities, and we select our dive ops on an al a carte basis. It's usually not intentional but it often works out that way, for us anyway.
During the first week of a Cayman dive vacation we tend to do snorkeling and shore diving on Grand Cayman. Depending on the weather we may add in a few boat dives. Since we usually travel during the slower seasons we haven't encountered any problem with finding space with many dive ops.
Most of the GC shore dive sites have an onsite dive op - so of course we use that shop. If we decide to dive the East End in the afternoon then we would naturally reach out to Ocean Frontiers because they are the only option, and they are good. For a morning dive on the East End either OF or Red Sail Tortuga dive operations would be fine with us.
If we want to do a "Special Dive" then we have to look for a shop that is offering a (Night, Kittiwake, Stingray City, etc.) trip on the day that we want to dive - because most dive shops only offer these special excursions a couple of times per week.
Sometimes we just want to check out a new dive op. Last year on GC we wanted to see the Cobalt Coast resort and dive with them - because we like the other Clearly Cayman resorts and the Reef Divers ops and we were interested in their new property on GC. They were great!
We do like some of the smaller dive ops like Cayman University Divers but small ops may book up quickly so occasionally we may have to look for someone else.
If we wanted to do a lot of diving on GC, we would book a package with one dive op - possibly a place that also offers shore diving - both for convenience and to get the best price and the most dives.
When we head over to Cayman Brac or Little Cayman for the second week of our vacation, we are mostly interested in boat diving, so staying at a diver-dedicated resort with an onsite dive op - and diving only with that op - is both convenient and economical.
I guess it sounds a little goofy but it works well for us!