I am an avid fan of Opera, and quite frankly, after testing it against Firefox, Chrome and Safari (lol IE), I will stick with Opera. Not only is the layout and design perfect for me (designed for Windows 7,) the speed at which Opera loads its pages seem faster than Firefox and Chrome. Furthermore, there are tests that say Chrome is faster, yet others say that Opera is faster. I'm willing to say that they're around equal, but I like Opera's layout much better.
Oh and some pages don't load properly, like hotmail. No biggie for me. I use Firefox for hotmail anyways.
Yup, after using Opera, I'd have to say, it's pretty much a layout/design preference that will make your ultimate choice. Both are lightning fast to a point where the difference may be in milliseconds, which doesn't matter. At least to me.