What's the difference between a discovery set and a subscription like Scentbird?

Discovery sets are one-time purchases that bundle a curated lineup, usually from a single house, in very small (1.5 to 2ml) vials. Subscription services ship larger (typically 8 to 9ml) decants of fragrances you choose each month, which is better for genuine wear-testing but locks you into a recurring charge and a limited catalog.