Which of the two approaches to routing a module settings page is the best practice?

Question

There seems to be two ways to link a route to a settings form for a module. I'm curious as to whether one is considered a better practice, and why.

_controller: '\Drupal\mymodule\Controller\MyController::myMethod'

or

_form: '\Drupal\mymodule\Form\mySettingsFormFile

Answer 1

Without knowing what is in the controller this would be the second one. The extra custom controller class only makes sense if you do something in myMethod() the form controller invoked by _form is not able to do.

See https://www.drupal.org/node/2117411#fapi-in-route

This integrates the form in a request so that it can receive route parameters and the request itself as well as returning a response if necessary.