I think that Atomicindy has a great suggestion.

I notice that in several of the locations I dived in thailand that there would be more than one dive company or tour operator on a boat.. seeing as how far the good dives are from the marina ( over an hour ) it definitely makes sense to take a full boat.

I Hate how crowded it is at coz (kind of like cairns in australia ).. where you have over a hundred divers on a site... I think having 12-18 wouldn't be too bad, although I prefer smaller groups.. I think a little give and take is in order.

I also agree that price isn't the main thing... service is huge.. when I'm paying top dollar to dive, all I want to do is show up, be given coffee and a light breakfast on the boat, double check my gear that has been set up for me... dive, have a great lunch and surface interval.. double check that my gear has been setup again correctly, then have another great dive... then crack open a few cold ones on the way back while the crew takes care of my gear.

Upon disembarking and seeing my gear has been taken care of.. Pull out the wallet and take care of the guys/gals who have been taking care of me all day.

then off for a postdive siesta and happy hour. now that's a perfect day.