Mozilla is better. Period.
You can also open your mail notification from LQ, click on the link, and the page loads up in your browser. Not sure if it works that way in general. Fewer clicks - your mail is right there. Don't need a newsreader, as mozilla does that, too. Etc.
Plus, Firebird is too damn much like IE. Mozilla's more like Netscape done right. You *can't* do IE right.