Use Firefox mainly due to it's ethos and it isn't part of the ever expanding google-sphere. Chrome is a nice browser which I think UI-wise is a bit nicer than Firefox (not much though) and I also like the process per tab design. It's nice being able to kill individuals tabs instead of having to kill the application.
I use both every day:<p>Firefox for regular sites I visit and stuff I keep open a long time (because of Tree-Style Tabs)<p>Chrome for my temporary / exploratory browsing (because when a website crashes it only takes out one tab instead of the whole browser).<p>I would prefer to use just one browser, if I could. But I am on the internet all day so horizontal tabs is just too painful when you have 20+ pages open all the time. And after a few times of losing your entire Firefox because of bad javascript on some random website, that gets unworkable also.
I prefer Firefox. With chrome, when my tabs increase more than 10, the system slows to a crawl. This happens with each subsequent update of Chrome. Firefox can handle hundreds of tabs without issue. Loading tabs on demand is a great feature for tab heavy users like me. Session restore is very reliable. So I dont mind those rare moments when firefox freezes. Using Chrome also creates this nagging fear at the back of my mind, as to how much info google collects about you.
I mostly use Firefox with two profiles, it has better memory footprint, more robust add-ons, the UI is customizable, tabs load on demand, and for me the mission is important too. Also, it doesn't spreads itself like a malware.
My secondary browser is Opera 12, but seeing how it does not get any kind of update, it is high time I ditch it for something else.
Neither. I'm currently using Opera 12 as my main browser, Chrome for websites that don't work with it and Firefox in case I need to use a proxy. None of the "new" browsers offer the complete package that Opera 12 does.
Pretty much the only reason I use Chrome over Firefox is because there is only one bar to type things into in Chrome, and it 'knows what I mean', where as Firefox has two and it never knows what I mean.