Well I use to think Firefox was the best until their recent update. It causes the little blinking line in front of your text to overlap while you're typing and it gets annoying, so I decided to switch to chrome.
Use to be FF but now moved on to Chrome. Much more sleeker and I find it quicker as well also the functionality if one tab freezes the other's are still good to use
I'm currently using Chromium OpenSource Web Browser, and it seems faster then other web browsers which is the browser which Chrome and RockMelt is based off of. It seems pretty fast, and stable.
I currently use firefox, and I've loved it ever since I started using it. It is very fast for me, and I use a web development plugin that helps in my web coding a bunch.
Firefox has had some problems with speed as people have said, but it has always been fixed for me with a quick restart of the program or computer.
I've actually used Firefox in the past but it was too slow somehow, so that was why I changed to Chrome. Right now, Chrome is still slightly faster, I think. But Firefox doesn't give me any crashes. I also like how tabs are managed in Firefox better - being able to scroll over instead of getting smaller sized tabs. That's all so far.
I think it's Chrome. I use it in both Windows and Linux. It's fast to start up, and loads pages quickly. I used to use Firefox, but it became to slow to load up.