It depends on what you like, really. Some of the sites that I least enjoyed were the channel dives. Because there were people in my group who couldn't "hot drop", due to difficulty clearing their ears, the crew were dropping us pretty far away from the areas where we could hook in and watch for pelagic life. As a result, we were spending those dives either drifting with, or kicking into current ... following an essentially lifeless wall for 30 minutes or so at between 70 and 90 feet until it was time to ascend. Those dives, to me, were a waste. On the other hand, the other two groups ... who were being dropped closer to the corners where the sharks and rays hung out ... enjoyed those sites a lot, and wanted to do more of them. As a result, some of our group decided they weren't worth the effort and just sat out the last few of them.
Looking through my dive logs, I could've skipped Thaa atoll altogether ... mostly what I logged was a lot of channel dives with heavy current, poor visibility and relatively dead reefs. Couple of interesting reef dives toward the end of the day, but not really worthwhile for a $7000 trip. And the one dive we did multiple times ... Rangali Madivaru on South Ari ... I could've skipped altogether. This is where they take people to see mantas ... but of the three dives we did here, we only saw mantas on the last one. But I didn't enjoy it because a LOT of boats go there ... the one time we saw mantas it was literally raining divers who were landing on each other, crawling around on the bottom, kicking and destroying what little coral hadn't already been destroyed ... it was not pleasant at all. The reef is trashed because of overuse, and it was impossible to get a decent picture because of all the flailing divers getting in the way. Frankly I just wanted out of there.
Laamu atoll had generally the best visibility and most interesting channel dives for my taste. But I most enjoyed the two wrecks we did ... Kuda Giri on South Male atoll and Machafushi on South Ari atoll. I thought those two dives were the best ones of the entire trip and would happily do them multiple times since you couldn't cover all of either site on a single dive anyway. Both wrecks sit next to very nice reefs ... Kuda Giri in particular was a place I could happily spend hours.
All of that said, you mentioned that you are going in August, which means you will likely be going north, rather than south as we did.
My recommendation would be to discuss with your group what kind of diving you want to do, and then discuss it with the crew. I can promise you that this crew works very hard to make sure that you have the best possible time ...
... Bob (Grateful Diver)