For security i think Mozilla is good. However, for simple mind and use, Google Chrome is the far more superior browser, after having a full browser window for a month it was hard to come back to mozilla or IE with their half windows.
Yeah, ive switched from using firefox 100% of the time to using chrome now, because i like how lightweight it is and its alot faster than what firefox/ie were.
Firefox and Safari on my Mac
IE7 on my servers
IE6 on my laptop (lazy, I know)
IE7 and Firefox on my Virtual XP machine
IE on my smartphone (haven't re-downloaded Firefox in some time)
Had Google Chrome on my last two boxes before I took them down and I liked it
So there's more than one answer. Though I will have to say, it's nice that firefox will work on all OSs and a smartphone. Chrome should be out for the Mac someday in the near future I believe and I'm sure for the smartphone too.