Mexico.

The default. Mexico's all-inclusive market is bigger than the next three countries combined, which makes it the first AI most American travelers ever book — and a destination where the variance between a great week and a wasted one is wider than anywhere else on the index. The scale is the headline and the trap: enormous selection, vast price spread, and quality that ranges from the highest-rated resort in the global index to the brand-recognition tax on a tired buffet.

Four Mexicos matter for the all-inclusive shopper. The Riviera Maya stretches south from Cancun to Tulum and packs the densest concentration of resorts anywhere in the world; competitive pressure here produces the best score-to-price across the index. Los Cabos sits on the Baja Pacific, skews adults-only and premium, and runs the better weather window from December through March, though the swimming is rougher than the Caribbean side. Puerto Vallarta and the Riviera Nayarit to its north is the older Pacific option, with Banderas Bay sheltering the bay. Cancun proper is loud, cheap, and the most likely place to lose money at the mid-tier.

What works in Mexico: direct flights from nearly every US hub, an all-inclusive product mature enough that even mid-priced properties get the basics right, and the deepest bench of standout boutique adults-only options in the global index — Grand Velas Boutique Los Cabos, Beloved Playa Mujeres, Palafitos, Secrets Maroma.

What to weigh: Riviera Maya room counts can hit 800-plus, and "all-inclusive" at that scale means a buffet at peak. Anything over 600 rooms requires a real read of recent reviews. The hurricane belt runs through the Yucatán and storms in September and October hit Cancun harder than the Pacific. Resort categories blur — RIU, Iberostar, Bahia Principe and the other volume operators often share branding across two-, three-, and four-star properties on the same beach, which makes the name alone a poor signal of what you're booking.

The honest filter: if Mexico is your default, the question isn't whether but where. Sort by value ratio for the Riviera Maya call; sort by score if Los Cabos is in play. The mid-tier in Cancun proper is where buyers' remorse lives.