Right now, I've got 23 "Miscellaneous" and only 16 "regular" quests. Sometimes, a Miscellaneous quest is just as complex and trying (if not more so) as some regular quests, and occasionally I believe one of the former will lead or turn into one of the latter.
The delineation between the two categories seems rather arbitrary to me so far. Is there some common criteria that separates them from each other?