Opera's quick, but its not fully supported by some sites. However, I love Opera Mini for mobile phone and other things.
Firefox = safest if you know how to tweak it well with the correct apps.
Google Chrome = loads the fastest opening it from the desktop. There's a few flaws: Apps are still in beta mode (Adblock doesn't actually block, but just clears it out after loading the page). Another thing is the privacy problem. You have to manually clear it after you're done with chrome, unless you start in incognito mode every time. But incognito mode doesn't have apps so adblock doesnt work at all.
IE = Great for standard use. If you're at work, you're suppose to use IE because those guys in the computer department are going to be like "We don't support Firefox," but they don't actually enforce it.
Google Chrome would be my choice once they finish the apps from beta mode and have auto clear of privacy things, instead of hitting ctrl shift delete everytime. (and yes, i'm a privacy freak)