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With this week's release of Firefox 3.1 Beta 2, a number of different writers have completed and published performance tests using the SunSpider JavaScript benchmark suite.

"Mozilla Corp. may have switched on a new JavaScript rendering engine in the just-released firefox 3.1 Beta 2, but the browser remains slower than preview versions of two rivals... the Dec. 7 build of WebKit is nearly twice as fast as Firefox 3.1 Beta 2, while the newest developer version of Chrome is about 40% faster," writes Computerworld's Gregg Keizer. "Both WebKit and Chrome - the latter relies on the former for its foundation - use the SquirrelFish Extreme JavaScript engine, a relatively recent upgrade that WebKit developers first unveiled in September. Firefox 3.1, on the other hand, includes Mozilla's new TraceMonkey JavaScript interpreter. Beta 2 is the first public preview to switch on TraceMonkey by default."

CNET's Stephen Shankland got slightly different results. "Though Firefox remains the leader on the SunSpider test, with a score of 2,110, Chrome edged very close with 2,140," he writes

And the results from AppScout's Michael Muchmore matched Shankland's. "In my results, Firefox 3.1 Beta 2 was nearly three times as fast as the released Version 3, taking just 2,689 ms compared with the earlier version's 6,535 ms," he writes. "By a small margin, it now beats Chrome, which came in at 2,763 ms."