Take a look at the screen shots below of Microsoft IE9 beta and Firefox 4 beta 6 and see if you can spot the difference.
The two browsers, more than ever before now look alike on the face value. Microsoft has simply continued reinventing the browser wheel. The download manager for Firefox is still more advanced. The browser history recall and closed tab recover is still better in Firefox. The dynamic nature of Firefox and its customizability is still unmatched. Microsoft in fact subtly conceded this in IE9 beta by offering to speed up the browser through switching off the add-ons. This is lame at best, because with all the add-on Firefox is still faster and crashes less often than the add-ons free IE9 beta.
download the two browsers here and test the platforms for yourself.
Download IE9 beta. Note that IE9 beta requires Windows 7 and will uninstall or upgrade your existing IE.
Download Firefox 4 beta 6. This is the recommended browser if you do not want to go through the trouble of testing both. In addition you can install it and use it without uninstalling your previous version of Firefox or any other browser you may have. And you do not need to install multiple pre-requisites and restart your computer several times to install a Firefox. Mozilla Firefox is still the best browser by far.