I would think that the severity of hypoxia depends on where in the body it happens. As far as I know (not much, admittedly) exhaling then counting to 60 is different than not allowing any oxygen into the brain. If you look at the Wikipedia page on Hypoxia you'll see a picture of a person with Hypoxia in their hand. Can't imagine your brain would do very well if the same thing occurred there.
Exhale and count to 60, and your brain keeps running off the oxygen still in your bloodstream. Evacuate your brain of blood, and it can't do that; as deaths go, this one would probably be faster than a neck tourniquet, but slower than the .50 BMG to the head I mentioned elsewhere in this thread. (How can St. Peter tell who died that way? They're the ones who ask him "What the hell was that?")
