If it's just for teaching some basic manners and giving you a bit more control in a situation then I don't think you can go far wrong with the dually halter. It isn't as harsh as some of the others and there's no poll pressure, which can make some horses go up or even over in some situations.
Oh Yann...........it's not poll pressure which causes horses to go up or even over...........its extremely bad handling, usually by people who have no idea what they're doing!
No halter in the right hands is harsh.........it's the handler using it harshly which causes problems.
If a horse tries to rear in a halter it is because someone is holding onto his head and trying to hold him down.............if the handler learns when to give timely release of the pressure it is fairly straight forward to dissuade a horse from rearing.
I get really frustrated when I take great pains to write long explanations (as I have done on this sight, and by PM's) of how to use pressure halters, and how to prevent horses from rearing, and how to load horses, only to see it all swept away by people who make generalised, sweeping statements such as yours.
Once the handler has perfected the technique required to handle horses with a pressure halter, and when the horse has had a proper fair introduction to such a halter, the transformation (in both horse and handler) is astounding.
The subtlety of the technique is such that a horse can be handled with a piece of string attached to the halter..........there is absolutely no need for any harshness with any pressure halter.
In the course of my work (as I've said before) I handle some extremely spoiled horses and change them into manageable, handleable animals in minutes. Surely that could not be achieved using harsh means.
