PHPStorm is a longstanding PHP IDE that has been extremely useful in the transition to OOP in Drupal 8.
VSCode is a recent IDE gaining in popularity, with a lot of support for PHP.
PHP costs $99 in the first year, $79 for the second, and $59 after that. VSCode is free, but can take some time to figure out which plugins you need.
What Drupal support are we looking for?
Code completion - Autocompletion on chained commands, services, etc.
File recognition - .module, .theme, etc.
Services - Detect service class from string for code completion.
Helpers - Config schema, routing, etc.