I use both Firefox and Chrome. But I prefer Firefox. Better addons and extensibility were already mentioned. But one thing that seems to be commonly overlook

I use both Firefox and Chrome. But I prefer Firefox. Better addons and extensibility were already mentioned. But one thing that seems to be commonly overlooked is the superior typography of Firefox. Firefox even does stuff like ligatures. That makes reading longer text much more pleasant. Firefox is also capable of handling large amounts of tabs. In Chrome the tab bar is of fixed length (length of the window) and thus the maximum number of tabs is limited by my screen width. In Firefox the tab bar can extend to the sides or even better you can use the TreeStyleTabs addon to organize tabs in a tree view. I think the biggest problem for Firefox was the long wait before FF4 was released. That was the exact time many people moved to Chrome. FF3.6 wasn't bad but was clearly slower than Chrome and had a huge memory appetite. Later versions improved this dramatically and Firefox now feels lighter/faster than Chrome. But every time FF vs. Chrome there are people claiming otherwise who have stopped using FF at version 3.6...