I like using software in my language. But when taking screenshots for blog posts or talking to an international audience, it's advisable to use the English interface. Switching languages is a quick and painless process in all browsers once you know how.
Increased security in web browsers can be a hindrance during development when all the infrastructure is not yet in place. For example, browsers don't allow insecure WebSocket connections from secure websites. This could block your development until you have a secure WebSocket endpoint available. Fortunately, there are ways to disable this security feature in all browsers.