Well, having never been to either I can't speak to the snorkelling but I can tell you from my research that Indonesia has some of the best, most untouched reefs in the world.
Here is my suggestion, if you are going to go through all that trouble to go to a place like either then I would strongly suggest getting certified with a PADI, NAUI, or SSI dive School. You are going to want to buy your own personal gear for the trip anyway so you might as well learn how to dive and rent a BC/Reg setup. and go see the beauty from the corals and fishes perspective.
Either way you will enjoy both places, and you are going to need to buy some gear so let us know how we can help get you on the right track.