Firefox.
I tried chrome, and its mix of lack of various features I use on a regular bases (I don't know, make a picture your wallpaper without downloading it, have it automatically open files for you, close a page without losing the thing your were downloading, exc) Makes it a major NO!
I'll stick with my well loved firefox (And Add-Block, auto pagerious(sp?), WOT, and Greesemonkey all come in handy. Not to mention themes)
I prefer functionality to speed, but when I feel like speed I open up minefield, thank you very much.
Also, Chrome seems to hate maximized, as it opens all its windows NOT Maximized. Very annowing.