Best diving in the area?

I dived a fair bit off Nosy Be, some great diving to be had off there. Several well run dive operations too. Nosy Tanikeli just off nosy Be is a marine reserve and worth the fee for a dive there. I've also dived many of the other places you mention and I still feel this is pretty good, especially if you see the manta rays etc. I've not dived Zanzibar or Mozambique so cant compare Mada to them. As said by others the east coast isn't as good.