Firefox on Android lags during scrolling on multiple sites that do not lag on Chrome. The only extension I have is UBO, and I don't know if that is the cause of it or not - I haven't tested thoroughly. One way or another there is a performance issue there by default.
Second, GrapheneOS has this to say about Firefox on mobile:
>Worst of all, Firefox does not have internal sandboxing on Android. This is despite the fact that Chromium semantic sandbox layer on Android is implemented via the OS isolatedProcess feature, which is a very easy to use boolean property for app service processes to provide strong isolation with only the ability to communicate with the app running them via the standard service API. Even in the desktop version, Firefox's sandbox is still substantially weaker (especially on Linux) and lacks full support for isolating sites from each other rather than only containing content as a whole. The sandbox has been gradually improving on the desktop but it isn't happening for their Android browser yet.
I'd love for both of these issues to be resolved at some point. But I stand by it because I like UBO and because I'm a bit contrarian.