One thing I like about subreddits though is that some of them feel more like an actual community--which is nice for a site as big as Reddit, because if it were all just one giant "community", it'd be harder to really find people to connect with based on shared interests and views. In small subreddits I'm able to have good discussions, I can recognize users and possibly remember things about them, and they each have their own distinct feel. I care a bit more about discussions generally than the content posted to a subreddit/tag. Bad moderation can make a subreddit go to hell of course, but I subscribe to a number of subreddits that I don't think have much of that problem. Good moderators take input from the community and act upon it.

Hubski I think is small enough that one big community works better than if it were to break up into many smaller communities. I like the tag system on Hubski and the subreddit system on Reddit, but I'm not sure I'd like it as much if it were vice versa.

One thing I like about the tag system is that it's possible to post something about a more niche interest and it can still gain attention. If you post something to a very tiny subreddit, then nobody will see it aside from the very few people that happen to have found that subreddit. On Hubski there's more than one way to come across a post though (2 tags + followers), so it's not so limiting.