Preformancewise is the latest IE (8) and Fx very much alike, but Fx is loading hmtl, javascript and flash faster if you run tests about it. And Fx is, which I find is it's real triumph, soooo much more customizable. There's millions of add-ons to firefox, just to tweak the look or preformance so it matches your personal use of a browser, or just separate programs like download tools, media players or even study programs that corporates with the internet perfectly. And then there's small, intelligent designs like the source code, filling the navigation bar with either the URL or banner of the website, improved session surfing, waaaaay higher security...
Conclusion: Fx > IE. Anyday.
I'm going to be blunt and say I don't give a hoot about any of that.
All I want is the freaking internet.