Apple released the latest major version of its Web browser, Safari 5, earlier this week. Along with several new features—one of them somewhat controversial—the update was said to pack a number of performance improvements, including DNS pre-fetching and optimizations to Safari's Nitro JavaScript engine.

“Safari continues to lead the pack in performance,” Apple SVP of worldwide marketing, Phil Schiller, said in a statement. We decided to put those claims to the test, pitting Safari against leading browsers on both Mac OS X and Windows 7.
Included in our tests are a number of JavaScript benchmarks, including the WebKit team's SunSpider, Google's V8 Benchmark, and Mozilla's Dromaeo. We also took a look at graphics acceleration performance using Microsoft's HTML5 “Flying Images” speed demo.
The tests were run on the latest stable versions of Safari, Chrome, Firefox, and Opera on Mac OS X 10.6.3 running on a 3.0GHz, 8-core Mac Pro with 10GB RAM and two ATI Radeon 2600XT GPUs.
The tests were also run on Windows 7 on a 2.67 GHz Core 2 Duo PC with 4 GB of RAM and an ATI 4830 GPU. On our Windows 7 rig we had a recent development build of Chrome (as opposed to the latest stable version), and we also ran the tests using IE8 and a developer preview of IE9.
Right off bat, our tests more or less confirmed Apple's JavaScript speed claims on Mac OS X. “Powered by the Nitro JavaScript engine, Safari 5 on the Mac runs JavaScript 30 percent faster than Safari 4, three percent faster than Chrome 5.0, and over twice as fast as Firefox 3.6,” according to a statement released by the company. We found Safari to be about four percent faster than Chrome, and slightly faster than Opera.
However, Firefox continues to lag significantly behind the other three browsers on raw JavaScript performance—Safari was nearly three times faster on our testbed.
(Source: Ars Technica)