Ease of integration into my native applications and the ease of tracking purchases across all platforms in one place. The documentation was extremely helpful to get set up and its pricing structure is transparent and perfect for the size of my app.
Really easy to use and the documentation is well written, and it helps a lot with the implementation. The simplicity of the integration and the business model, they give you all the features for free until you reach 2k monthly recurring revenue. And the customer support is really efficient. I'm using RevenueCat in all my projects.