Firefox vs internet explorer:
I'm not an IE user but FFX has a lot of issues
First, it does not start fast when it is loaded from the disk. For my 3 yr old computer, it takes about 10 or more seconds to start it, unlike the browser I use Opera it takes much less time to start.
Plug-ins i frequently use such as Adobe Flash Player does not perfrom well in FFX. The flash movie often stops in FX unlike in Opera which plays flash movies smoothly.
Lastly, Firefox is still young. I guess it is much better than IE. But for me Opera is still the best.