I was surprised too, I'd expect those numbers to be roughly equal. The only thing I can think of is that they're using Flash for audio. The Flash runtime has run better on Windows than other platforms for a while. Would be curious to see those numbers with the HTML-5 audio forced to true to see if they stay the same.

note also the specs of each of those tests; the windows tests have i5/i7 chips with at least 4gb of ram. The Lion test is a dual core with 2gb. That's not a fair test, so the whole table is bogus.

In the video they talk of profiling it in IE — maybe it wasn't profiled and improved in other OSes/browsers.