I've always used Chrome and I really prefer it, but I'm forced to use Firefox since a year ago because my chrome is completely full of undeletable adware. Seriously, even the computer geeks at my local i-fix-your-pc-store couldn't help me. And since I'm not planning on making enormous amounts of back-ups so I can put my pc to default settings I'll just stick with Firefox until I've a new laptop.
Damn you JOOniiCiouponn and CheapMeo >:c
I've found that I can do things on one browser that I might not be able to do on another, so I switch between Firefox and Chrome, depending on what websites I plan on visiting and what I want to use the browser for.
Definitely Chrome. Firefox is slow, Safari just wasn't my thing, and IE is just all around an awful browser. Chrome is fast and simple, you can't go wrong.
Opera is my primary browser, though I keep two or three on all my computers. Each have their own benefits but Opera has always been my favorite. I want tab-stacking back though, I miss it.