I would say run with Nova if you want to code Erlang. If you want to code Elixir choose Phoenix. In the end both are based on Cowboy.
We started to create Nova from the lack of frameworks on the Erlang side. We wanted a fast way to start new web application and start writing on your app instead of spending time on setup.
Elixir have always had good tooling and framework from the start.
Being blunt, if you're new to Beam, I'd probably choose Elixir and Phoenix. But Elixir isn't for everyone, and if you prefer Erlang's syntax or are interested in contributing to some of the projects written specifically in Erlang, then that's what you should pick.
Both are great, but I think Elixir is more beginner-friendly. Through the course of learning one though, you'll inevitably see some of the other, which is pretty cool. :)
We started to create Nova from the lack of frameworks on the Erlang side. We wanted a fast way to start new web application and start writing on your app instead of spending time on setup.
Elixir have always had good tooling and framework from the start.