I think I've been using the terminology incorrectly, or at least ambiguously, but it seems I'm not alone -- every definition I can find of the terms "choke" and "strangle" says that they are used both for compression of the carotid or jugular, and blocking of the airway. I think, however, that my answer is the same regardless of which you're talking about. One is fast, the other is slow, both are potentially deadly. If you interrupt the flow of oxygenated blood to the brain by means swift or slow, you're messing with someone's life. Unless you like the thought of filling out a lot of forms, explaining yourself to someone's next of kin, and spending a lot of time in court, you'd better not play games like this.
My working definition is that a choke compresses the airway, a strangle compresses blood vessels, if applied in complete accordance with the definition. But perfection is elusive, and a badly applied (but comparatively safe) strangle can slide into a badly applied (and comparatively risky) choke, especially with a resistant subject and an adrenalized individual applying the strangle.
As for speed of effect, the difference between fast and slow lies primarily in the skill level of the individual applying the technique. There are some individuals who can not only control how fast the subject passes out, but how much or how little the subject fouls himself.
The effect of a strangle, which was long ascribed to interrupting the flow of oxygenated blood to the brain, is now more generally believed to be an autonomic response to signals from baroreceptors in the neck, an explanation which accounts for fast strangles in a way the lack of oxygen theory doesn't.
All that said, it's a good idea to have someone on hand who knows basic resuscitation techniques if that's what you're practicing.