IE is on its seventh version while Firefox is still on version 2.5 or so. My dad says that Firefox is a bug, and IE works just fine. He's a computer technician.
IE is actually on the same level as Firefox and maybe higher. Its controls are harder to work and figure out, but it has more security stuff hanging around.
Ex. Some sites were blocked (not any inappropriate ones, mind you <.<;;) by my dad by going to Tools --> Internet Options and such. I tried reversing it, but I couldn't, since I needed a password.
Firefox, on the other hand, can't block any sites.
Firefox is fast, reliable, and its controls are easier to work out than on IE, but on the family computer, it caused some problems when I tried working on Microsoft Word and using Firefox at the same time. Dad tried working on Word and IE at the same time and it worked.
I suggest you try both Intenet browsers and see which one fits you. The descriptions I gave above are just little summaries to what you can find out and discover on your own. :)
P.S. I also suggest trying Opera. I haven't tried it yet, but I hear that the reviews are generally very positive.