1) Both Restfox and Hoppscotch run completely within the browser without needing a backend server to process the http requests.
2) Restfox has a plugin system. Hoppscotch currently does not have a plugin system but they're in the process of adding it.
3) Hoppscotch doesn't support for nested environment variables since it follows Postman rather than Insomnia.
4) Restfox can import exports from Postman and Insomnia. Hoppscotch can also do this but you might struggle to find their import button.
5) Restfox does not have GraphQL or WebSocket support.
6) Compared to Hoppscotch, you'll notice the UI is much more straightforward and gets out of your way. Gives you the familiarity of the desktop http clients you're used to. But this is my personal opinion.