In my opinion, Elixir and Phoenix will give you a better experience with BEAM and OTP, excellent tooling, a more mature ecosystem, and one of the best web frameworks ever to exist. I think Gleam is cool, but I can't see trading these benefits in for static typing.
To be fair, I can't think of anything I care less about than static typing, so please keep that in mind when entertaining my opinion.
I also preferred dynamic typing, until my complex rails app grew to the point I didn't dare to do any refactoring.
But I didn't switch opinion until I discovered ML type systems, which really allow for fearless refactoring. At occasion there's some battling to satisfy the typesystem, but even with that I'm more productive once the app grows in complexity.
I thought I'd share my experience, not trying to convince anyone ; - )
To be fair, I can't think of anything I care less about than static typing, so please keep that in mind when entertaining my opinion.