This might sound odd: I think the simplicity promotes more depth in the links and discussion. I mean, this looks like one of the stack exchanges, which regularly see discussion from top people in certain STEM fields. On reddit, there's thumbnails (this is a big one), upvote/downvote counters in two contrasting colors, a single quantity of net votes, and so on. Reddit, which I try to use as a discussion forum, is in many respects more suited as purely a social media website with some commetning ability. I came to Reddit from other forums, one's with avatars and no good way of knowing if someone replied to your posts. The discussion on those was tremendously bad compared to Reddit. There seems to be an inverse correlation between flashiness and discussion quality.
I don't necessarily agree that Hubski allows more freedom to choose a browsing experience. I think Reddit and Hubski both do this well, Reddit especially with the recent "multi-reddit" changes. Sure, the default subreddits aren't very good, but the strength of Reddit lies in the ability to subscribe to certain subreddits and ignore others. I can effectively use Reddit by entirely ignoring the goings-on in r/atheism, r/pics, and r/gaming.
I think one obvious disadvantage and advantage is size. Hubski is considerably smaller. This can be a disadvantage. For example, the physics tag isn't very robust yet. It can also be an advantage. For example, the funny/humor tag isn't loaded with garbage.
Something I like about Hubski is the ability to follow people. You can do this on Reddit too, but it's pretty far removed from the traditional Reddit experience and I'd wager most people aren't aware you can even do it. Hubski is different in that it's promoted as a key feature. If people followed me, I'd feel more obligated to post good content.
Less concrete: Hubski sort of feels like a mature Reddit. I also feel like I can much more easily "waste time" on Reddit than I can on Hubski, which is good for Hubski. Lastly, I'll be perfectly honest and admit that there's a certain charm to smaller communities.