This is a test on Ubuntu so obviously Internet Explorer will be excluded. Safari and Opera aren't open source so they're left out too. We're looking at open source browsers on the Gnome desktop. I've picked these four: Firefox 4, Chromium, Midori, and Epiphany.
For the record, I think Epiphany will be chosen (if there's a change) since it's the default browser in Gnome anyway and so fits in with Ubuntu's wish for a six month release cycle.
HTML5 isn't officially out yet, but clearly all the big players are pushing for it so here we have it. It's the HTML5 standards test.
Firefox trails behind a bit, but I wouldn't worry too much about it. With Firefox 5 expected to be out soon and Mozilla on a faster release cycle, things should improve rapidly. Besides, it'll be a while before very many websites make HTML5 a requirement. It's only the more recent browsers that have really pushed for HTML5 support.
The Acid3 Test
Acid3 is supposed to show how well a browser supports various CSS features. Here's how things stand with the four browsers.
|From top left moving clockwise: Midori, Epiphany, Firefox 4, Chromium|
And Chromium wins it's own V8 benchmark, as expected.
Firefox 4 and Chromium are close enough in SunSpider to be indistinguishable in actual performance.
Neither Midori nor Epiphany stood a chance against the two giants here, but they'd still work well in real life, I think. Benchmarks are never definite, after all. All we know are raw numbers that don't necessarily translate well into reality.
In terms of flexibility, neither Epiphany nor Midori supports plugins of any kind. At least, it's not made visible in the browser itself. Plugins is definitely Firefox's traditional strength just as perceived speed is Chromium's.
So there you have it.