Having discovered that Chrome has pinnable "app" tabs, too, I've moved back to Chrome, for three reasons.
1) It's WAAAAAY faster
2) Typing stuff in the address bar consistently loads Google search results for that stuff, whereas Firefox does sometimes, and other times it'll load whatever site it deems the best match. While I'm sure that's configurable, I'd rather not have to hunt for it.
3) The thumbnails of my most frequent sites is really quite useful. There's a plugin to do this for Firefox, but it doesn't actually do this - you have to manually add each site.
These are all pretty minor things, and of course I'll still have to use Firefox while developing.
definitely chrome has the best performance. my choise is chrome. vote at http://coolometer.org/chrome-vs-firefox
Firefox has much more plugins available and a wider community. I use them both on a daily basis, the main issue I have with Firefox is its memory management - rather lack of. It leaks memory, and frequently takes up 1.2 gigs on my computer, while Chrome with more tabs, takes less than half of that.