This is mostly to just downmark the sites that are loading 800 images and 34 megs of javascript like many news sites, hopefully to encourage them to make things a little lighter. ^.^
Chrome’s pagespeed tests have been pretty accurate for what I’ve seen at least both in chrome-based browsers and firefox. Like my sites load in a fraction of a second for everything, but some other sites definitely take 10-20 seconds with a lot of jumping around as it loads… ^.^;
Safari and Chrome both use the same rendering engine for note, it’s their javascript engines that differ so that is where you should see the differences.