I think everyone are using the FireFox for security and for the speed in Firefox and only few numbers are using the IE because of unsecured and it is also too old.
Firefox is far better than IE. It's faster than IE and has a better interface even. It has better ad-ons and tools than in IE.
There's no doubt Firefox would win this. It's 100x better than I.E. But if you had added chrome to the list, it would have surpassed Firefox sadly. But nothing beats firefox tbh. The flexibility and the range of plugins available on Firefox cannot be matched.
I will certainly go for Firefox. I never prefer to use I.E. Some other browsers may run at the same rhythm.
Given between these 2 choices, I will definitely go for firefox. It is more stable and it has better add-ons. However, I have switched to Google Chrome as I find it to be very fast and responsive, better than fire!