I've used Chrome ever since I first tried it, virtually. It's just easy to me. I went through a period when I tried to switch to Firefox once, but it's so much slower. I think that might just be because of my computer, though, but nonetheless I had to go back to Chrome.
However, the biggest potential advantage I see in Firefox is how customizable it is, but I've never put enough effort into that for it to make a difference. Plus, Chrome is customizable too but I only use a couple extensions, so that factor apparently isn't all too important to me.