There appears to me that there is some belief the best way to make a working dog leave the bite is by chocking off. I do not believe this is the best method. I believe that in the case of an operational bite where you have to get the dog to leave the bite quickly, it may possibly be but if used all the time in conjunction with the verbal leave/out command in a training situation it can causes more problems than not. I am of the opinion that if you confuse the chock off with a leave technique you end up with a dog that starts to type writer bite or becomes more reluctant to let go and you create a conflict situation with the dog. The chock off is a method used to build bite drive and not the opposite. This is not to say that in a situation where you need to get the dog off in a difficult operational circumstance that it should not be used. It should only be saved for this situation or for building bite drive. In all training situations a leave or out command coupled with a suitable physical correction is the best method followed by a win on the desired behaviour.
This link from Leeburg Kennels is well worth watching if you are interested in this topic. http://leerburg.com/flix/player.php/205/Michael_Ellis_on_Choking_a_Dog_Off_the_Bite_to_Get_Him_to_Out