I went with Big Island Divers a couple years ago. It was an awesome time. I don't think going with a big crowd is necessarily a bad thing for the manta dive. All the dive operators head to the same area, so as said before, even off a small boat, there will be a lot of people in the water. The more light, though, the more krill, and the more mantas! You will be blown away by the trip no matter who you go with, though! I did several days of diving with Big Island Divers, though, and had a great time with them all week.