I have been to both places...Ambergris and Placencia. They have very different atmospheres. Ambergris has the mood of really having a lot to do, being very tourist oriented, with a lot of services, restaurants and conveniences. Placencia, at least the village itself, is more of a mellow fishing village that has started recently to have more tourism, but is not as tourist oriented, in my opinion, as Ambergris. That makes it more mellow, laid back. The beach in Placencia is gorgeous (sea grass though!), and really gives you a chance to RELAX. You could spend the whole day lolling on the beach, reading in a hammock, just chillin!!! Ambergris has more "stuff" goin on. BUT, I have not been back to Placencia since Hurricane Iris, and I dont' know how much they've rebuilt. They BOTH have their charms. It just depends on what you want. You can do snorkeling, scuba, nature hikes, at both places.