I use both when needed, but I prefer Firefox for the simple reason that I'm used to it (lol). Many have been saying that Chrome is faster than FF, but that's not the case with mine which I can't understand. Anyway, both are much better than IE, so yeah...
I am some sort of fan of Chrome. As for me it is a ready browser. Everything works fine for me. I have used Firefox before, however its crashes and slows we driving me crazy. Chrome lacks tons of useful extensions that Firefox has, however its speed and stability are just what I need.