Re: aikido vs jiu-jitsu
Royce Gracie was asked at a seminar "How do you get out of a choke?".
He used the analogy of getting punched in the face. "Once your hit it's to late".
The key is not to get in the choke in the first place.
If your are in a full mount by a jui-jitsu expert, it's to late. I don't think anyone on this thread, (or their instructor) can escape it using only aikido techniques.