It all depends on what you want out of the holiday
Dive trip vs beach trip with diving.
If dedicated dive trip, then Ocean Frontiers, Cobalt are great choices. both are way off the beaten track.
If you want beach and diving, then IMO, rent a condo along Seven Mile Beach strip and go out boat diving daily with one of the west/north side operators. They all pick up and drop off. There are good options for shore diving not too far away at Lighthouse and Sundivers as well.
Our usual routine is morning boat diving then afternoon and or night shore diving at Sundivers.
I personally like the condos at Christopher Columbus and Anchorage as they are at the north (quiet) end of the beach and are priced better than many of the others in shoulder and low seasons. I don't like Sunshine Suites particularly as not on the water. Being in a condo allows you to make your own meals if you want as well as having much more space than a hotel room. Both of the condos I have mentioned above are relatively small developments with spacious beach and pool areas. You would need a car if staying there as not much in the way of restaurants in walking distance.
If you are OK with iron shore, then Bonnies Arch condos is a good option as they have their own dive site off shore. I've never stayed at Lighthouse Point but they also have a dive shop and dive site.
My personal preference for operators on GC is DNS Diving, Big boats, small groups. Everyone has their own bias and favorite op. Other people seem to like Dive Tech, Living The Dream, Wall to Wall, Divers Down and Deep Blue among others. All the operators are good or they wouldn't stay in business in a very competitive environment.
Lots of choices on Grand and hard to go wrong.
