Busy.org definitely has the more appealing interface, the better post editor, and those nice "social" features that you mentioned in your post. However, I find it more difficult to navigate through busy, as it is harder to find tags that interest you and sort by "hot", "new", or "trending" (as in steemit). Additionally, it is more cumbersome to transfer funds on busy (or not even possible on mobile). But an advantage is that you can actually see the fund transfer memos on busy mobile, as opposed to steemit mobile.
Conclusions: It's a close race, but I find myself coming back to steemit.com each time I use busy.org for a while. None of these two really think of the end-user, though. Both should put some more serious effort into UX design (and finally release an App).