Today there has been a lot of misinformation going around the Internet. It all started with the otherwise reputable Anandtech tech reviews website, which actually may be a bit at fault too here for starting all this, but most of the blame should really go to everyone who has read this information ALL WRONG.
If you take a look at this site right here, you'll see that Galaxy S II should in fact be significantly faster than the iPhone 4S when it uses a more current browser like Firefox or Opera Mobile. You can expect the upcoming "stock" browser in Android 4.0 ICS (possibly the Chrome browser) to be even faster than that, making Android's browser perhaps twice as fast on a GS II than on an iPhone 4S.
Besides the older browser and older JS engine, one other reason why the Android browser may not be as fast is because it apparently doesn't use both cores, which is unfortunate, and it's a shame that Google didn't enable that since Android 2.3 (Opera and Firefox seem to use both).
So iPhone 4S may get to have some bragging rights for a couple of weeks (undeserved), but once Nexus Prime arrives with Android 4.0, and all future ICS phones, should be significantly faster than iPhone 4S, and that's a long time to wait until July-October next year.