Here's our experiences:
Cozumel (5x)- all dives DM led, everyone goes up together, boat picks up
Nekton liveaboard (2x)- dive on your own, no DM in water, do your own thing, must navigate back to boat
Palau Eco liveaboard - all dives done from skiff, DM led - sometimes 4 DMs in water with 15 divers, boat picks up. Never swim out into blue water as current can and will take you out to sea. All divers must have signaling device and need them!
Bonaire - all boat dives DM led out and back to boat, shore dives on your own
Hawaii - all dives DM led out and back to boat
Keys - dive on your own, no DM in water, do your own thing, must navigate back to boat
SE Fla - drift dives carrying flag, boat picks up; on wreck dives the boat is moored and you must navigate back, no DM in water either way.
Calif (4x)- boat is moored, all dives on your own, no DM in water, must navigate back to boat, through kelp! If you have air left, never surface away from boat - it is dangerous to try to swim on top of kelp (special briefing given on how to do the "kelp crawl"). Always approach the boat underwater if possible.
Local fresh-water diving (200+ dives) - all shore diving, have fun!
Personally, I have started to dislike the "follow the DM" type of diving. California (our first trip there was in 2004) was such a liberating experience! Bonaire was fabulous for the same reason. I like being treated like a self-sufficient adult. In Palau it was necessary to hang with the DMs, because of current and many dives done from reef hooks. Other than that, I think we are now planning trips with that in mind - if diving allows you to dive on your own without DM leading, yeah!