If you want to party at MyBar, have fairly easy access to restaurants in Georgetown and along Seven Mile Beach, then Sunset House is probably for you. If you prefer a quieter place with excellent accomodations, much better shore diving, excellent food between dives and your choice of comradery with or solitude from other divers, then Cobalt Coast should be your choice. My wife and I have stayed at both. We keep going back to Cobalt Coast.
Going to Cobalt Coast is like going to see old friends, even if it's the first time. Restaurant staff, Divetech staff and DMs and Dora and Arie at the front desk are more than accomodating. The rooms are much nicer than Sunset House. Each one is like a suite, with a separate bedroom and sitting room with a hide-away sofa.
I recommend the meal plan. If you add up the cost of meals ($60 US per person per day) and compare that to the cost of rental car and restaurants in US dollars, you'll be money ahead. But, it's not just money. Dinner comes with appetiser, entree and dessert. The variety -- from calimari and conch fritters to hamburgers to Indian curry to English fish and chips to the daily specials and soups -- all are excellent. You won't find better north of the Ritz.
As for diving; with Sunset House, you'll be diving the West Wall and the South Wall. Personally, of the two, I like the South Wall better because you won't be hearing cruise ship anchors clanking through the water, you won't have to compete for sites with all the other dive operations on Seven Mile, you won't have "submarines" chasing you off the reef if you dive near Georgetown. But, this time of year, if you stay at Cobalt Coast, you'll be diving the spectacular North Wall, which I think offers the best variety and most dramatic wall dives on Cayman. Ask to go to Ghost Mountain.
The better shore diving will be with Cobalt Coast/Divetech. Lighthouse Point has one of the nicest, easiest to access shore dives (and night dives) on the island. Three weeks ago, my wife and I saw a minimum of one turtle every time we dove Lighthouse or Cobalt. On one night dive at Cobalt Coast I saw the usual reef fish, large lobsters and crabs along with Slipper Lobster, Spotted and Green Morarys (2 each), an octopus, a Yellow Stingray, a large Porcupinefish, a juvenile Drum and squid.
Since staying at Cobalt Coast, my wife and I talk about , "next time, let's try someplace different," until one of us asks, "Why?" And, we realize that when you consider all that you get, there's no other place that offers better.