What's all that noise? For me Firefox just works fine on everything...
I can't even remember when or why I went with Firefox, must have been really early days.
But ever since, I've just seen no reason to change. IE was garbage and Chromium had one giant disadvantage: it was made by Google.
And it's just deeply unhealthy to have all parts of an eco-system owned by a single company. Same with Edge or Safari.
If Firefox were to publish their own OS (as they did at one point), I'd probably run Chromium on that, just because I consider balance of powers essential, to society in general, and to my software environment.
I run a lot of systems, dozens, really, physical and virtual, spread across Linux, Android and Windows. And I need browser access on nearly every one.
And I want consistency, same layout, behaviour etc. when I switch between them.
Well, at least as much as possible; there are some differences between a mobile phone and anything desktop (even with a touch screen), that are implied by the form factor.
Firefox delivers that, Edge is a no-go, Brave comes close (and is often the 2nd option), I gave up on Opera when it became Chinese and the phones became powerful enough to handle Firefox.
Of course, I dislike having to disable all the money makers like Google search or that "Pocket recommendations" stuff every time I run a freshly installed Firefox, but even that is a lot faster, when it's pretty consistent across OSs and versions.
I don't understand the "Firefox is garbage" allegations: everything I do on the Internet works as expected, except where sites get too snoopy or refuse the ad-blockers, which I obviously run with pretty much all filters enabled for sanity.
And those sites I'm happy not to revisit, unless it's the government and I have to (with the ad-blocker disabled).
I got the whole family on Firefox, too, and it's been easy probably because I started them there long ago, before Chrome or Edge became as aggressive (and repulsive) as they are today.
If it were to go away, that would be very hard indeed, much like finally letting go of Microsoft Office completely and finally embracing StarOffice, sorry LibreOffice despite its quirks.
Functional or performance differences that I noticed have been very rare.
Google Maps in the 3D Globe view is really impressive in terms of how much it's able to squeeze out of relatively modest hardware. For the longest time I've been astonished on how it would render the neighborhood much better (in terms of accuracy) and much faster (in terms of speed) on a modest Atom system even at 4k than Microsoft Flightsimulator on an RTX 4090.
But for the Atom (or smaller ARM SBC) I generally had to use Chromium to get that speed, Firefox stuttered on these smaller systems, while I never noticed anything wrong on my normal "desktop" or "worktation" class machines.
Even that has changed now, I can't see any noticeable disadvantage for Firefox e.g. on Raspberies 4 or 5 with the current software.
Where I actually *do* see a disadvantage for the Chrome based browsers is on WASM, where it regularly detects and uses less than the full set of cores on machines with lots of cores and threads.
Yes, only Chromium at the moment seems to enable WebGPU, but once that becomes popular enough, hopefully that will change: I'd really like to see WASM being able to take advantage of the GPU as well, but hardware independance and the ability to exploit ISA extensions and accelerators are rather too conflicting to sort out easily.