I am a die-hard Explorer Ventures fan, and have my fourth trip booked for October. You will get everything you're looking for and more if you do the Turks & Caicos trip. I can't speak to the other trips as I haven't taken them, but the T&C boat is superb and has always been staffed with people who take really good care of you. And the food is excellent for sure if Stan's still there.
I have had one ExVen disappointment, however, and it was a big one. We took the Bahamas trip two years ago and honestly, I wish I could have gotten my money back. The boat was due to be taken out of service right after our trip and it should never have made the trip at all. Stuff broke all week long (including water heaters, so warm showers were iffy) which was a source of daily frustration; I don't know when the engineer ever slept, because he always had multiple failures to manage -- if it wasn't for him, the trip wouldn't have been possible. The bad energy seemed to radiate out to the staff as well, as the captain had a baffling pattern of taking us regularly into the only pockets of bad weather that he could find, and the rest of the crew seemed generally demoralized.
The lesson I took from this is that for live-aboard diving, a lot depends on the quality of the boat itself, and it pays to investigate that to the extent that you can. I'd recommend sticking with boats that are either newer or recently refitted.
Live-aboard diving has ruined me, I'm afraid. Resort-based diving can't begin to touch the dollar/dive ratio that live-aboards give you, and if you have a decent boat, it's surprisingly easy to spend a full week with a bunch of other people in what would seem to be limited space. I guess jumping into the ocean every couple hours helps.
There is so much diving available, in fact, that you may well be tired for a couple of days before you adjust to the pace (you don't have to do every dive, of course). I always find it amusing when the call comes for the next dive and there's almost a group-groan, like, "Oh man, is it time to go back in already??" Tough problem to have. I can't wait for October.