Everyone has their favorite...and everyone is right.
Most ops will let you charter your own boat with a minimum of 4 divers. We did that with Dive with Martin and it was only $10 more each for the 2 tank trip. The benefit was the boat was waiting on us when we arrived and we were in control of the day. We were all brand new divers and we did not have to worry about an advanced diver having to go on lower risk dives with us. For the situation we were in, it worked out better than perfect and we had an awesome first Caribbean dive. Dive With Martin runs out of the International Pier which may be convenient. I believe they will store your gear for multiple day dives. they are one of the oldest dive operators on the Island and have lasted for good reason.
Most operators will use the smaller "6 Pack" boats so # of divers should not be a problem if you do not charter your own. We dove with Blue Magic in January and had a great trip. They took care of all our gear so we did not have to lug it back and forth which made it very nice. they run out of the Caletta Marina which is far south of town. They usually leave from their dive shop and pay for the cab to the marina, but if you are close to the marina, I'm sure you could meet them there. If your resort has a pier, they may be able to pick you up there.
Most of the operations are very close in service and price but here are a few differences you may want to ask about. Email several operators in advance so you can have all the details worked out.
1. Big boat or small boat, max # of divers
2. Where do they leave from, can they pick you up at an alternate pier?
3. Surface interval- On the boat, at a beach, or at a beach club?
4. Tanks- aluminum or steel and what size is available
5. Computer dives or time limits- Surface as a group or with your buddy based on personal computers/ air remaining?
6. Rental BCD- Weight integrated or weight belt?
7. Time of departure
8. Night dives? Book one if you haven't!!
All of the operators listed have good reputations and I personally know people that have used most of then with great reports. I do not know if Blue XTsea has been listed but Christy is the owner and a frequent contributor to this board. I plan on giving her a shot on our next trip.
Don't forget a surface signal device and SMB. On one drift dive our group of 6 divers were scattered over quiet a distance. I had to duck behind a corral head for my wife to catch up and we spent the rest of the dive with one of us holding the others BCD D-ring. Lots of fun, but easy to see how divers get scattered too.
While your there, please drink a Bohemia Obscura (or 10) for me, eat the scallops at Guidos, and Alex at the Thirsty Cougar makes the best mojito I've ever had (order it shaken and strained)
Safe travels!!
Jay