I use Firefox on both Mac and Windows because of its extensions. Firefox allows its extensions to change more of the browser experience than other browsers do.

I really love Tab Utilities (https://addons.mozilla.org/en-US/firefox/addon/tab-utilities...), which helps me use my browser despite my 914 open tabs by making the New Tab command open the new tab directly to the right of the current tab, not all the way at the right. Other extensions that can only exist in Firefox include Copy Urls Expert (http://www.kashiif.com/firefox-extensions/copy-urls-expert/) and Tree Style Tab (https://addons.mozilla.org/en-US/firefox/addon/tree-style-ta...).