Pour ceux qui parlent anglais, voici une page qui peut être intéressante :
http://en.wikipedia.org/wiki/Comparison_of_web_browsers
Sinon pour ce qui est de Safari, apparemment le navigateur aurait une vitesse bien supérieure aux compétiteurs lors de l'utilisation de Javascript :
Is Safari faster?
At the release of Safari 3 beta for Windows, there were several claims about Safari's page load performance. It was giving results that showed it was clearly faster than other browsers. Since I generally like to check things for myself instead of trusting what companies say, I gave the new Safari a whirl. Sure enough it was very fast. Its CSS was quick, its page loading was quick, its JavaScript was quick. Perhaps quick, but certainly not as fast as they seemed to claim it was.
I have a variety of machines that I tested it on, and all showed the same thing; it was fast, but not really faster than the competition (Opera, for example, but other browsers were also faster in some cases). But when tests used JavaScript to check the page loading speed, Safari produced numbers far smaller than other browsers, even though the actual page load was not faster when tested with a stopwatch. Simple CSS float tests would produce times of less than 100ms, while the actual page load (from disk, so no network lag is involved) could take as much as 5 seconds.
http://www.howtocreate.co.uk/safaribenchmarks.html