I just got back from provo this afternoon. I did three days of 2-tank dives... one day with dive provo and two with caicos adventures. These two were the only dive ops open this month (slow season). I was signed up with caicos adventures for the whole trip, but they had boat problems the first day so they put me on dive provo's boat. Both were great, and I would be comfortable with either.
On my first day Dive provo brought us to Northwest point from the Turtle Cove marina. CA leaves from the south side and we went to French Cay on day 2 and West Caicos on Day 3. While we were at French Cay, the Dive provo boat showed up... so it seems where you end up diving really just depends on where they feel like going that day. I gotta say, the ride out of the south side was sooooo nice. Shallow turquoise water the entire ride with water so clear, you can count starfish on the sea floor while the boat is flying by. We even saw dolphins during the ride and took a few minutes to circle the boat to watch them.
I really don't think you can go wrong with either Dive op. When I go back, I will probably go with caicos adventures again only because I'd rather leave out of the south side. Leaving from Turtle cove didn't make the trip any shorter (I thought it would)... either way you are looking at a 45min boat ride to the dive site.
My favorite site was the Gully at West Caicos.... a neat swim-through section of the reef and a curious reef shark following us around the entire dive made it quite interesting. The other dive sites were great too... just gotta hope the big fish show up. I saw quite a few sharks (nurse and reef sharks), turtles, stingrays, and a huge eagle ray. The structure of the walls were pretty neat... We dove the Crack (NW point), which is a crack in the wall that you can swim between, and Amphitheater (NW point) which has a "scooped out" section. All the walls were steep and deep... they just looked like they dropped forever.
Visibility post-Irene was about 50 ft at NW point and about 80 ft at French cay and West caicos. Should be better when you go if these damn hurricanes stay away. These are all wall dives, and most start at about 50ft, so you are looking at dives in the 60-90ft range. If you stay in that depth range, Nitrox can help keep you from reaching your no-deco limits on your second dive. They ask that you don't go deeper than 100ft, but one guy went down the 130ft (by himself!:crazyeye

The dives in French cay and West caicos had some current we swam into on our first tank, so our second dives both days were drift dives.
PM me if you have any questions...