I currently have Chrome, Firefox, and Opera installed.
I almost never use Opera except for occasional testing purposes. In my opinion Firefox has some advantages over Chrome. The "back-end" is more user friendly and easier to configure and, as stated before, there are some nice add-ons and other useful features not available on other popular browsers. However, I get a lot of unwanted popups on Firefox despite making adjustments to settings and using add-ons designed to prevent popups. I almost never see popups in Chrome with the default settings. I have found that, (at least on my computer and OS), that Chrome loads and runs much faster than Firefox and I also like the built in translation feature of Chrome.