Firefox started out nicely, but then they hit a bad spill where it was using resource like water and crashing on people.... That bad spill is what people remember and why people shy away.
Today Firefox is stable and no longer uses resources. Chrome is good for small things like checking e-mail, but if you're using it for a longer time it will eat up memory (CPU after a while as well).
Although Chrome still has a better web debug tool. Frefox's tool is small and hard to read. Also isn't as straight forward, but Chrome is.