They are all free. I usually use Firefox, but I've also got IE8, Chrome, Opera, and Safari.
Like it has been stated several times, it's all a matter of personal preference. Just download several and see which one you like. Unless, you are really tight on HD space, none of the browsers really take up that much space, and if you just got a new computer, I'm guessing you have plenty of free HD space
You will also find out that some browsers work better on some sites than others.
One advantage of having several browsers, is that if you are having a problem on a particular site, you can try another browser to see if it works better.