I was never a huge user of reddit or 4chan - so I can't speak with absolute authority on the matter. But I'll say this:

Why should you use hubski?

-community. the people here are thoughtful, considerate, challenging, and intelligent. theadvancedapes, kleinbl00, and too many others to name are people that I may not see eye to eye with on political, social, or political issues - but that's the beauty of hubski - we can have intelligent informed discussions that broaden my perspective and increase my understanding. Seldom do conversations devolve into the standard internet flame wars. The few times I felt offended by something, I approached the individual in PM, and came to an understanding. Maybe it's the smallish user base, maybe it's the general tone - but this place seems to remain downright civil.

-content. sure... we get the occassionaly cat video or other meme... but for the most part, that stuff stays on reddit/4chan/digg, etc. and the quality content flows here. And by customizing your feed, the noise stays at an almost inperceptable level.

-admins. mk, thenewgreen, and others are incredibly responsive. This started as a side project for them. They make no money from the site. They are more communicative and responsive than services I actually pay for. They listen to, and even make system wide UI changes based on a user feedback.