PS: Some of the differences are just funny. Retric in Google = Hacker News profile, Retric in Bing = Slashdot Profile.
Slashdot has been around for over a decade. It has a PageRank of 9 versus 6 for HN. I would imagine Bing has a similar metric for measuring the popularity of a site. It seems to make sense that the Slashdot profile would rank higher.
What I think is really interesting is why Google ranked the HN profile higher. I'm thinking freshness is weighted much higher on Google than it is on Bing. I've done similar searches on both and while both yield relevant results I'm more likely to see older content on Bing.
PS: Some of the differences are just funny. Retric in Google = Hacker News profile, Retric in Bing = Slashdot Profile.