In general JSDoc is just much more verbose and has more friction, even outside complex types. I recently finished a small (20 files/3000 lines), strictly typed JS project using full JSDoc, and I really miss the experience of using the real TypeScript syntax. Pain points: annotating function parameter types (especially anonymous function), intermediate variable type and automatic type-only import, these are the ones that I can remember. Yes you can get 99% there with JSDoc and .d.ts files, but that's painful.