I'm not too impressed with PeaceKeeper and the way it test a browser's speed and load-bearing capability. It basically tests the browser for its ability to handle JavaScript functions and the load based by commonly used JavaScript modules, and these commonly used JavaScript modules and functions are to the discretion of PeaceKepeer. If you think about this realistically, depending on users choices and what websites they browse, it's possible that for some Opera is better suited than Firefox, and for some Firefox is better suited than Opera.
Ever since Chrome has launched the Developer built-in package, I've been pretty impressed with it and I can't seem to be able to stop using it. Firefox on the other hand allows people who need heavy customization and Opera boasts of being a "fast" browser, with nothing except all of these weird tests to support it. When it comes to people using these browsers, I've ever actually heard anyone say that Opera loads faster than Chrome. Eventually, if Opera loads a page in 2.81s and Chrome loads it in 3.02s, does it really matter? That 0.2s isn't going to make much of a difference when it comes to being comfortable with your browser and with the other functions that it provides.