Hi
I'm not a Maldives expert, but I'll try to help you with what I know.
First of all, it depends on what time of year you're planning to dive there. It's all a question of the seasons.
Second, from what I know (mainly books on the dive sites of the Maldives), the dive sites on Gan didn't get high ratings as the ones in the other atols.
What do I suggest? Keep looking for info, or even buy books about scuba diving in the Maldives. Just don't get all the way down to the equator and get disappointed....