To be honest, this isn't the post I have been planning in my head. That post has to do with the three phases of approaching the Shekhinah, as mentioned in the Zohar, as an analogy for coming to know the Higher Self. That one will have to wait. Instead this was inspired by some recent reading. I have been going through a book by the late W.E. Butler (whose books I highly recommend, especially if you're a Dion Fortune fan). He was discussing clairvoyance and precognition in a way that is essentially how I see divination working.
He described it like catching glimpses from a very high window to the street below. From this perspective you can see all sorts of things going on. For instance you can see a man in a suit, though his features would be indistinct from that height. He's walking down the side walk. You can also see a painter high above the sidewalk, but still below you. The painter drops his bucket of paint and you can see that the falling paint can is in the path of the man on the sidewalk. Then the blinds on the window go down and that's it. Now, from your perspective, and by doing a little mental math, it seemed more likely than not that the man on the sidewalk was going to get splattered with paint or even get hit by the bucket. That's what you can predict from what you've seen. However you have no way of actually knowing this will happen. Perhaps he will stop to talk to someone, perhaps he will turn into a building, perhaps he will get knocked down. The permutations are nearly infinite. That's kind of like what divination is like.
Prophecy is something different. There are, it would seem, in fact two varieties of prophecy. The first might be considered "passive," the second "active." The terms aren't perfect but they'll have to do. The passive form is what you find in the Bible or Qur'an. Think Abraham, Moses or Mohammad. Yes, they actively participated in God's work for them, but they didn't go out and seek divine revelation; it was thrust upon them. This kind of prophecy isn't what I'm going to talk about. It is what it is, but without your friendly neighborhood deity there to initiate it, it doesn't really matter what its like.
The second form is also Biblical and represents the later schools of prophets but is also discussed by Sufis such as Al Ghazali. Here the prophet, through various mystical techniques, purposefully seeks visions of . . . whatever. These tends towards being funky, mind you, because they work differently from divination. In divination you are looking through time and space and just seeing it from a superior, but still limited, perspective. With this kind of prophecy you are viewing things from an even more superior perspective, but one that is outside of time and space. Sort of like getting a God's eye-view. It is therefore unlimited as well, or at least effectively so. The problem is that eventually you come back to yourself (a state of sobriety, in Sufi terminology), which is very much in space and time. This means things have to be translated from one view to another, from spirit to soul, as it were. Thus the funkiness of this kind of prophetic vision. The brain just isn't designed to deal with that kind of thing.
Those aren't the only differences, of course, but it is what caught in my mind.