http://www.pcworld.com/article/167065/what_to_look_for_in_firefox_35.html
check the comments for more battles in the Browser War... always someone who doesn't comment on the article, but instead says "Opera is better than all of them" etc.
Small tip.. I you have been upgrading for a long time or keeping the same profile launch in safe mode and clear your about config settings to their defaults.. You will loose custom settings in some add-ons but this lead to a significant speed boost for me.