In high-schooland still occasionally I experience bouts of extreme insomnia, I loved it and hated it. I've gone 70+ hours with no sleep and also no drugs in my body, i.e. no meth, etc. Around the 24-30 hour mark my brain function would actually increase. I could do things faster, think clearer and came up with some really good ideas during those times. Approaching 40 hours my words start to come out jumbled, not like a drunk, but out of order sometimes. I would start to make jokes that seemed hilarious to me and just be in a general state of hysterics for the most part. 50 hours the physical aspect would start to kick in, blurry vision, muscle fatigue etc. During these times though I would rest my body but my mind would not be able to sleep. I made sure I drank plenty of water and did moderate exercise.
This time frame for the most part is during school weeks, weekends etc. So normal days. 60+ hours is visual and auditory hallucinations. I would be playing Counter-Strike in a darkened room at night, quit the game and go into another room and still see the silhouettes from the players as if they were in front of me. Real enough for me to take a fighting stance like someone had broken in my house. I would hear the gunfire from the game at random, 'Fire in the Hole' and look over my shoulder to see if a flash bang was coming in. At this point I was afraid to drive, I basically couldn't do anything. Edward Norton put it best in Fight Club, "With insomnia you're not really awake, and not really asleep" or something to that extent.
Anyways, those conditions are much, much, more easy to cope with than that of forced deprivation, i.e. water being thrown on you when you nod off, stress positions, for example being in a confined space where you can't stand up but can't lay down, or having to lean against a wall with your head pressed up against it, bent at the waist. So my vote goes for water boarding. I believe it would yield information faster, but may not have the same reliability for accurate information as sleep deprivation.
I heard some time back the British were having great success with an unusual technique. It involved putting the prisoner in a room of all one color. Lets say blue. Blue lighting, blue walls, blue everything, food, clothes etc. They would keep them in there and awake with limited amounts of sleep for a set time then move them to another colored room. Rinse repeat. I'm not sure of the psychology behind this one but it sounds interesting.