I don't just eat at one restaurant, why would I visit just one website? There's room for all of them and different places satisfy different needs. Many Hubskiers are redditors and both sites satisfy different things for them. Right now, Hubski is pretty small, so trying to get really granular, regional information isn't all that doable. For example, if I follow #Detroit on Hubski, I'll get some random posts, but nothing as abundant as /r/Detroit. Both sites have value, imo. I use reddit more to go find some info on a topic. I use Hubski to be a part of a community that I'm likely to interact with on an ongoing basis.
This is sort of my view on it. Hubski is good for talking to people, but it seems to be "talk about things that 18-25 year old American liberals would be interested in." It's pretty heavy sometimes. I agree with you on the interaction bit, though. I'm never going to move out of lurking on Reddit.