Re: BJJ vs. Aikido
I was taught - in several dfferent places, that a choke blocked off the air (trachea) and that a strangle stopped the flow of blood (ans I still follow this distinction). Of course, you might like to think you can get both at the same time but I was also taught in Judo that the wise artist aims for only one.
Also, once any choke or strangle is 'on' properly it's all over - you can't get out of it. The trick to get out of any such hold is to do so while it is in the process of being applied, which ultimately depeneds upon your skill. If the hold against you is 'on', you obviously do not have the skill, otherwise you would not have ended up in that position.
As a point of note, a good strangle or choke does not hurt at all. If it does, something is amiss.