Well, as a Firefox user, I surely could sound very biased, but as for my main browser FF is still the best.
Surely there are great options, depending your needs, for example Ungoogled Chromium or Brave Browser, if you're looking for something that gives a Chrome-like experience, but without all the data gathering from Google (Ungoogled Chromium) or with some privacy-minded features already integrated (Brave).
There's also Waterfox, which is a Firefox fork (I can be wrong with this description! But that is how I understand it) that is still compatible with the old addons (XUL). There's also another project on GitLab named LibreWolf that it will be (or already is) a Firefox fork that (based on the Librefox project), in a similar fashion to Ungoogled Chromium), it has removed several mozilla-only features such as the integrated telemetry, and I think that also the "studies" feature. It also attempts to integrate some privacy-minded features in a similar way that Brave browser do. As the last time that I checked the project, they already have created some builds for Linux. I'm not quite sure if they have started to work on OSx/Windows builds.
I don't know which are your parameters to determine which browser could be better than Firefox, but it could help to take a look at those (and perhaps other) projects, use them for a while, and see which of them suits better for you.
Surely there are great options, depending your needs, for example Ungoogled Chromium or Brave Browser, if you're looking for something that gives a Chrome-like experience, but without all the data gathering from Google (Ungoogled Chromium) or with some privacy-minded features already integrated (Brave).
There's also Waterfox, which is a Firefox fork (I can be wrong with this description! But that is how I understand it) that is still compatible with the old addons (XUL). There's also another project on GitLab named LibreWolf that it will be (or already is) a Firefox fork that (based on the Librefox project), in a similar fashion to Ungoogled Chromium), it has removed several mozilla-only features such as the integrated telemetry, and I think that also the "studies" feature. It also attempts to integrate some privacy-minded features in a similar way that Brave browser do. As the last time that I checked the project, they already have created some builds for Linux. I'm not quite sure if they have started to work on OSx/Windows builds.
I don't know which are your parameters to determine which browser could be better than Firefox, but it could help to take a look at those (and perhaps other) projects, use them for a while, and see which of them suits better for you.
Links:
Ungoogled Chromium: https://github.com/Eloston/ungoogled-chromium
Brave Browser: https://brave.com/
Waterfox: https://www.waterfox.net/
LibreWolf: https://gitlab.com/librewolf-community
Kind regards.