I've dove at Lighthouse, and visited the resort by boat, but not stayed there or dove with them. From what I could tell, it is MUCH smaller than Fantasy Island. My guess is there is probably a maximum of 20 or so guests at one time, so I doubt you could call it a cattle boat. They are at the north end, and some of the more well-known dives are at the south end - it's probably 20 to 30 minutes to get to Half Moon or Longs.
I was recently at Turneffe with a couple who had stayed on Lighthouse - they said the dive ops were very similar (though the lodging and food were better at Turneffe according to them). In any event, this is how it worked at Turneffe:
When you arrive, you grab a tank and rig it exactly how you like it. From then on, the only thing you have to clean or worry about is your mask & wetsuit - they'll handle the rest - cleaning, rinsing, drying, etc. I've been diving over 25 years - on both ends (working and vacationing), and I love valet diving. It doesn't remove the responsibility for giving your gear the once-over before you strap it on, but having someone else haul it around is great. Of course, it's up to you. You can tell them to let you do it and they will. 1 guy started that way, but by the 2nd day, he was a convert too.
Most of the sites at Turneffe are 5 minutes away, including the Elbow. For those, they usually put 6 to 8 in an open boat. You go over the side, dive where you wish, then signal the boat when you surface - the capt will come and get you where you are. It was not unusual to have the groups head in different directions, and the dive briefings covered what you would see where. There was little current or swell - maybe they do it differently if present. TIL boasts something like a 75% return rate. When we were there, there were only 13 guests, and 22 staff - talk about service!
When we went to the Blue Hole, it was in a 50' covered boat that was dry and comfortable for the 90 minute trip - not like most of the boats we saw there that left San Pedro at 6 in the morning for 2.5 - 3 hour ride!
If you're interested in Turneffe, their site is
www.turneffelodge.com - I can't recommend them highly enough.