Is that your opinion or do you have some facts to back that up?
Yeah Tom's Hardware, the biggest and most respected site for hardware and software benchmarking, http://www.tomshardware.com/reviews/opera-10.60-internet-explorer-9-safari-5,2680-12.html in their second Web Browser Gran Prix of 2010. http://www.tomshardware.com/reviews/firefox-chrome-opera,2558-10.html.
In both tests, Firefox is also beaten by Opera (as well as Chrome). In one of the tests, it is also beaten by Safari, and in the latter test it 'ties' with Safari.
Personal preferences aside, these are the best and most accurate objective facts available, for those areas which can be objectively measured.