YAML had a fuckton of sugar, where JSON has as little as possible, but the biggest differentiator is that YAML has references — you can express cyclic graphs. T

YAML had a fuckton of sugar, where JSON has as little as possible, but the biggest differentiator is that YAML has references — you can express cyclic graphs. That's why it's a natural fit for fixtures and seed data in Rails: it natively handles relational data.