Flinto is better with Sketch, and Principle is better with Figma. Flinto has better structuring of work (reusable behaviors, transitions AND components) and I'd argue that it's easier to work in and understand how your project is flowing. Principle feels more like a quick and dirty way of creating interactive prototypes. I find the arrows showing flows in Principle extremely difficult to follow in larger projects.
Flinto is better with Sketch, and Principle is better with Figma. Flinto has better structuring of work (reusable behaviors, transitions AND components) and I'd argue that it's easier to work in and understand how your project is flowing. Principle feels more like a quick and dirty way of creating interactive prototypes. I find the arrows showing flows in Principle extremely difficult to follow in larger projects.