I’d like to know what are your opinion between building a Web App using embedded Elixir/Phoenix (.eex files), where the data is being passed with the render function to the template, like so:

<%= if @var do %>
  It is obviously true
<% else %>
  This will never appear
<% end %>

vs. separating the frontend (with Javascript and AngularJS maybe) from the backend, using Phoenix to serve a RESTful API:

$http({method: 'GET', url: '/some/phoenix/api/resource'})

What are the advantages and situations where each one is better suited? Are there any use cases where they should be mixed? (particularly does Phoenix mix well with Angular?)

For a simple information system, I think embedded is more than enough but for more modular, better structured and to allow frontend and backend developers to work concurrently the latter is better. Also, separating makes the backend development easier since you just have to build on the :api pipeline instead of both :browser and :api pipelines.

The main disadvantage (for me at least) when separating the frontend from the backend is to have to use a lot of Javascript which I personally hate and find difficult.