Answers:
in my opinion, definately firefox. it is known for being faster and safer, and blocks all popups. it also offers tab browsing, which is very useful. firefox also offers a ton of extensions to suit your needs, and themes to suit your mood.
the only advantage Internet Explorer has is if your viewing Internet Explorer-only pages. but firefox has an extension that takes care of that too
Personally, I love Firefox, but I do not have it at home. I love being able to make tabs and stuff. I've also heard that it is faster.
as you know ie has been is part of the operative system now, this means that if you have windows you can make lots of things that firefox doesnt, like search in your pc directly using ie, i guess that it depends in your point of view, if you like going against the system use ff, it charges a little faster cause it does not provide all of the things i mentioned before, ie has a plugin which enables you to create tabs as if you were in ff. :)
actually internet explorer is better! did you see internet explorer 7 in windows vista It's amazing