Most of the people here keep falling over for opera, so heres a proper benchmark done for all 5 of the top browsers (including opera 10.5)
http://www.tomshardware.com/reviews/firefox-chrome-opera,2558.html
BTW if you dont want to go into reading the entire article this should be enough of a hint:
http://www.tomshardware.com/reviews/firefox-chrome-opera,2558.html
BTW if you dont want to go into reading the entire article this should be enough of a hint: