I wouldn't stay anywhere but Scuba Club.
I've been to Coz about 20 times, Scuba Club is still our #1 place.
We also stayed at Fiesta Americana a few times because we could use Hilton points to stay for free, but their beachside has since closed and we haven't been back to F.A.
I've been on night dives all around the world - New England, Florida, Cozumel, Honduras, Caymans, Bonaire, Turks & Caicos, Great Barrier Reef, Palau, Maldives, Thailand, etc
Paradise Reef in Cozumel has given us the best night dives that we have ever experienced. It's not good 100% of the time but it's still pretty darn good.
There is a really cool batik shop near the plaza on Calle Adolfo Rosado Salas. "Mayan Batik Factory." Be sure to stop in, say hola to Carlos, and buy cool T-shirt.