The 20-hour layover
I love long layovers, they allow you to explore a bit more than just the airport. If time isn't an issue, this is definitely the way to go.
It's basically buy 1 get 2 (or 3--depending on how many you can squeeze in) free.
Another bonus: the cost of airfare with long layovers are often lower.
Plus, with KLM offering a free city 'layover tour' in Amsterdam to customers, long layovers are a thing.
When I had the opportunity to pick between a long layover in Mexico DF and an extra half-day in Japan, I opted for the layover in Mexico.
Here's what a 20-hour stint in Mexico looked like.