Agreed. But don't read too much in RBS details yet. RBI is currently very early and will need to change substantially learning from experience of actually typechecking real codebases. Stripe and Shopify are helping with this.

RBS has better syntax, but has features that don't have clear semantics or feasible implementation. And doesn't support inline annotations that are necessary in practice.

RBI is limited by ruby syntax and thus isn't as nice, but has good semantics and support inline annotations. And has been tried on hundreds of real codebases including those with dozens of millions lines of code.

We'll need to gather benefits of both on our way forward.