Which is Faster? Internet Explorer 7 or FireFox 2?

I have been using Flock browser for a while. I like it very much. Flock is based on FireFox. I also use Internet Explorer 7 and Firefox 2. I use Windows Vista. Recently I have noticed that many webpages load and layout the page faster in Internet Explorer than in Firefox or Flock. I have not done any scientific testing, but my eyes feel so!

Why would IE load faster? I think because (1) Internet Explorer works well with Windows as it share the core in common. (2) Internet Explorer handles unclosed tags and uses its own intelligence for laying out webpages. (3)I found that IE has taken less memory than FF2 or Flock when loaded 10 tabs.

(I promote FF and Flock than IE, and continue to use Flock.)

How is it for you? Which browser do you prefer for browsing the Internet and why?