For me unread and recent are pretty much the same, they are both sorted by last post time, the only difference is once you read a topic it disappeares from /unread. On /recent the title changes color if its read. Also /unread is only useful if the forum isn't busy. Once you have an active forum /unread and /recent are pretty much the same.
We had some discussions internally too about merging unread into recent(move the unread count to the /recent icon) and the change /unread to be a list of topics from people you follow.
Not final decision yet though.