Reel Crazy14:I dove with Ocean Divers in Key Largo. They ran a good operation. But if you arent interested in cattle boats then i have heard some good things about the six pack boats. I stayed at the marina del mar hotel which wasnt luxurious but clean and comfortable. The Islander in Islamorada is right on the ocean with some comfortable rooms for a modest price.
I like Ocean Divers as well. As for cattle boats, a couple of thoughts. You can interact and observe other divers and learn from them (not all divers are good examples though). It will be more comfortable for you on a larger boat if it is your first time out on the ocean. You'll have more room to don your gear, and the ride will be smoother (seasickness). On a big boat, you can walk around after the dive, lay down to rest, and will have plenty of room to stow your gear. 6-pak boats, little center counsole boats with outboards, can be a little trickier for a new diver. They can be cramped if 6 divers are onboard. You'll be doing a backroll off the gunall instead of a giant stride off the swimplatform. Not a big deal, but you probably didn't practice it in your pool dives. Getting back in a 6-pak can be trickier as well depending on the type of ladder and it's positioning next to the outboard engines.
Anyway, these are some of the differences between the larger boats of Ocean Divers and the smaller 6-pak's. Everyone has their own preferences. The best situation is a big boat with only 6 divers!