I think a big factor, at least down here in the Riviera Maya, is the accessibility and variety of food and drinks at the boutique hotels. Some of the most beautiful smaller hotels can be quite isolated and if you are not planning on organizing transportation to the nearby town, the costs can add up fast for your guests (even though the room will be cheaper). If you are planning a hotel that is more centrally located, let's say close to Playa del Carmen, for example, there are infinite options for eating and drinking at all budget levels. Another thought consideration would be the package deals you can arrange with a travel agent. Including airfare and an AI hotel in a package (especially in off seasons) can lower the price dramatically. Happy Planning!!