Most recent, reliable benchmark I could find:
Browser Comparison Benchmark Results.
Only a month old.
You can see performance for yourself.
False statements in this thread:
Chrome uses less memory than Firefox. Opera is faster than Firefox and Chrome.
True statements in this thread:
Chrome is (generally) faster than Firefox.
I personally prefer Firefox, since I <3 customization. I like being able to do whatever I want to do with my browser. I could run a more barebones version if I cared about speed more, but it's fast enough and it does everything I want it to do. Including everything that I like about Chrome.
If all you care about is speed, and don't give a damn about what you can make a browser do, then probably Chrome is the way to go.