I use Firefox on desktop, tablet, and mobile.
Why Firefox
I use Firefox at least partially because I still remember absolutely freaking out as a teenager over tabbed browsing. I’ve been using Firefox pretty much since it came out. I’ve stuck with it through some performance issues in the past — maybe a smarter person would’ve switched during those times, but I’m glad I never did. And at this point, I’ve been using it long enough that it’d have to become unusable for me to quit.
Customization
I also find Firefox more configurable and customizable than Chrome. I can do whatever I want with Firefox and make it look exactly like I want it to look. I honestly don’t fiddle that much or use themes or anything, but it’s super nice being able to shift items around, make stuff I don’t use disappear, etc. For example — I like having the file manager available without needing to press the “ALT” button to show it every time. This takes only a second in Firefox, and greatly increases my user experience (I’m able to drag the menu bar from one window to the other much more easily).
Tab Behavior
One of the biggest advantages Firefox has for me is its tab behavior. I strongly prefer the way Firefox behaves with many tabs open. Chrome annoys me because when you open enough tabs, it crushes the tab in your bar down. It does it to the point that you can’t click the X to close it and it becomes Olympic Precise Mouse Movement Gymnastics trying to get to the tab you want. I’m not a super-heavy tab user but I typically have enough open that Chrome’s smashing down the tabs bothers me.
Gripes (To Be Fair)
Pretty much my only major gripe about Firefox is the inability to right click on the program’s file menu and close a window. This is useful primarily on smaller windows where it requires more precision to hit the “x” button rather than simply yanking it to the upper right-most corner on a full-screen window.
Other Browsers
I do use Chrome pretty consistently for logging into multiple accounts on one site. I have also used Chrome as my primary browser at work before. I’m not completely unfamiliar with Chrome, and it is my secondary browser of choice. I’m not as familiar at all with Opera, Safari, or Internet Explorer, though I do use them as far as testing goes.
Chrome
A few things annoy me in Chrome. As aforementioned, Chrome’s tab behavior is a huge downer for me.
The bookmarks bar shortcut irritates me off to no end because I constantly accidentally tap it when opening new incognito windows. When using Chrome as a primary browser, it took me a while to even figure out that was what was happening — I thought my bookmarks bar was just randomly disappearing, and I didn’t know there was a shortcut (no thanks to Chrome — I had to go into settings every time to “Always show bookmarks bar” and if there had been a hint there like “Hey, press CTRL + SHIFT + B”…).
More than anything, I don’t use Chrome because I think it’s really important to have browser diversity. It’s disheartening when stuff is broken in Firefox and works in Chrome. It’s relatively rare, but it happens — some people don’t bother with browser prefixing anymore. Added, the “Best Viewed in Chrome” thing is becoming more frequent (as mentioned in a recent r/webdev thread). A lot of people don’t seem to realize there are other options beyond IE and Chrome, even. I’m only one person, so I’m not significant or anything — but I continue to use Firefox and promote it wherever possible.
Developer Tools
I do prefer Chrome’s Developer Tools. There are a few different features in Chrome’s devtools that Firefox lacks. For one, the Responsive Design Mode is better in that I can emulate actual devices and their screen sizes. There’s also a neat feature where you can simulate a slower connection.
Browser Choice
I do think it’s fine to use whatever works for you. I’d never berate someone for using another browser, obviously — although I might suggest an upgrade for those still running outdated versions of IE! Otherwise, I’m not opinionated on what other people use, in all honesty — as long as there is a choice of browser.