I've been to the Big Island several times over the last two years and have used four dive operations.
Kona Divers, Big Island Divers, and Kona Honu are all based out of the same small boat harbor. In my experience, all three were good dive operations. Over the course of my first two trips to the island, I found that all essentially hit the same dive locations and use the same dive profile. I attempted to book long range trips with all three companies to see some different areas, but had little success. I enjoyed diving with all three outfits, but felt I was a better fit with the Kona Divers crew.
During my trip last summer, I booked with Kohala Divers. I was pleased with the operation and thrilled to see some different dive locations. I also booked a couple of days with Kona Divers during that trip; I enjoyed diving with them.
I had planned to dive with Jack's Dive Locker during my trip last summer as well; however, I managed to tear-up one of my hands while shallow water snorkeling with sea turtles. The local ER doc patched me up and banned me from diving during my last two diving days on the island. Jack's has an excellent reputation and I'm sure I'll dive with them sometime in the near future. I personally know a lot of divers who have been very satisfied with Jack's.
Depending on the length of your stay, you might want to spread out your diving business. Do a few days with a company out of Kona and a few days up north with Kohala. Insure that you'll see some different areas.
Perspectives vary, but I don't really like the dive profile any of the companies use. Profiles typically involve reef tours that start shallow, drop deep in the neighborhood of one hundred feet, and a return to the boat in shallow water. As a serious photographer, I have little interest in dropping below fifty feet. I'd rather stay shallower where more subjects are available. Next time I go, I'll probably inquire about hiring a private dive master who can hang with me while I do my thing.
The night manta dive is an experience beyond belief. I suggest booking it twice during your trip; once at the front end of your trip and once towards the tail end. On the chance that no mantas show-up or the dive gets cancelled for your first try, your second booking gives you another shot.
I don't have any experience with Hawaiian Scuba Shack.
Hope your trip goes well. My wife and I have really enjoyed ourselves while on the Big Island. It's an amazing place. We look forward to returning.
-AZTinman