No steel tanks, nobody there like Aldora. Dumb down your expectations or you're in for a world of disappointment. Aldora does more diving in a month as a single op in Cozumel than all the dive ops combined on Isla Mujeres do in a year. It's a very, very small dive community on Isla Mujeres.
The diving in Cozumel is very consistently good. The diving in Isla Mujeres is like a jagged graph with massive peaks of awesome dives with a whale shark, manta rays, hammer heads, dolphins, eagle rays along with the valleys of boring dives that make you wonder why you even bothered...
In general the diving around Isla Mujeres is sub-par to Cozumel, but because some of the sites are more open ocean like, the chances of seeing anything are possible. So you could spend a week with nothing to tell but stories of boring dives or you could spend a week diving there and have a tale of just an awesome encounter that won't be duplicated in Cozumel no matter how many times you dive there.
