Here is a video comparing the 3gs to the 4s for internet browsing speed. The complicated sites are much different the simple sites are basically the same:
It seems a little deceptive to test highly complicated sites like apple.com, since you're not going to have a good experience on sites like that no matter how fast they load. The vast majority of the sites I visit on my phone are text-based: HN, Reddit, Google News, 538, DailyKos, RealClearPolitics, etc. On these sites there wouldn't be much difference at all. If I want to go to apple.com I'll do it on my laptop regardless of speed.
And based on the video, it looks like the 3GS is as fast or faster than the 4S for sites that are text-based or optimized for mobile.
http://www.youtube.com/watch?v=HuSYkdyfuTA
I expected it to be more of a blowout on ALL sites. I can't tell if this proves you right or wrong.