All browsers now are almost equivalent: I couldn't say what's better.
Now I'm on Chrome that was very fast the first days I used it, but once you start with plug-ins, favorites, cache and so on gets slower (when loaded the first time in a session) like the others.
The advantage of Chrome is that you type your search in the address bar without calling Google, but I don't like much the Ctrl-F fucntion to find a word in the page: I find it less friendly than Firefox.
Talking about safety, once both Firefox and Google were immune because they had a small market share.
Now the're comparable to IE so hackers are putting efforts in attacking them too.
IE 9 is now a state of the art browser with the advantage of being continuosly updated in terms of solving safety issues by simply using Windows update.
You need to have a genuine Windows , though