This was not true before Wilma, but now my favorite one-two is Punta Sur Sur (that's the southern part of the Punta Sur Reef) followed by Santa Rosa Wall.
My reasoning is this--I am a swim through and large animal junkie and have been that way since 1992! Back then it was very hard to get any operator to take me to those places--that is why I am in the situation I am in now.
Prior to Wilma my favorite first dive was Columbia Deep but Wilma opened so many new swim throughs (flushing out eons of sand build up) that there are now twice as many at Punta Sur Sur, big and small. Perhaps the wierdest thing is that proir to Wilma it was the best place to see sharks but they were the usually small black tips. Haven't seen a black tip since, but we now routinely see fairly large Caribbean Reef sharks and ocasionally the Great Hammerhead (see the October Issue of Scuba Diving Mag). Really, before Wilma we had never ever seen a Caribbean Reef Shark here! And done on nitrox with dive computers, you can do the Devil's Thoat as a grand finale! This is now, in my opinion and by my standards, the best dive in the Western Hemisphere.
For the second dive I vote for Santa Rosa Wall. It can be best enjoyed at depths no deeper than 80 feet, has lots of great swim throughs, and offers much of the same grand architecture as Palancar and Punta Sur. But the best part is the shallow parts after you finish the wall. There you can find all kinds of new fish habitat scoured out of the sand by Wilma's waves and spend the last part of your dive in shallow water, offgassing and having a very enjoyable safety stop. And vitually no one dives this area, so the really shy creatures abound.
Dave Dillehay
Aldora Divers