Browser performance all boils down to the add ons you have for each, and the longer you have them installed, the more crap wants to attach itself to your browser. Google Chrome is an excellent choice, as is Firefox. IE9 made some huge steps forward.

Say what you will about IE, there are just some things that WON'T run on anything but. Test me on this one. Blame it on lazy web designers pandering to Micro$oft or whatever else, but IE has to be on my computer for compatibility.