This is the direct link from my results page:
http://www.google.com/search?btnG=1&q=where+does+software+update+download+files?
If you want to save the updates for some reason, like to install them on multiple systems without re-downloading, it's best to download the updates from Apple's web site. The packages you get from the built-in Software Update are tailored to your specific system (to minimize download size), so they might not work on other systems. The packages you get from Apple's web site are designed to work on a wide range of systems.
That link gives me the Windows-centric results, same as before. Which doesn't surprise me, really, since there's nothing in the search terms to suggest you're looking for Mac sites, and "software update" is a general term. I usually throw "mac os x" (in quotes) into my search phrase when looking for Mac stuff, otherwise all I get is Windows links.
I'm still confused as to why we're getting different results. Are you logged into your Google account? Maybe Google knows you're a Mac guy and adjusts your results accordingly.
FWIW, on my system they're saved in ~/Downloads, not /Library/Updates. But maybe that's just when I select "download only" intending to actually install them later when I'm ready to reboot.
That wouldn't explain it, though. THE OS variable on your MacBook should be the same as mine on all my Macs. Just checked on my iMac: Same thing. Even changed the system language to English just for trying. Same thing.
The only explanation I can come up with is that all of your computers are set up incorrectly and you're all insane, while my MacBook is running perfectly and I'm totally sane.
So you're running LittleSnitch then? I'm doing that as well. I'm not filtering any google-stuff, though.