I agree with franknbeans. For trail riding, I won't use anything without a throatlatch. All it takes is one head shake or the horse rubbing his head on something to get the headstall off. I think they are fine for arena riding or showing though.
I have one without a throat latch and I have had my horse ditch it with a head shake at least three times. Of course, I do have him in a snaffle which doesn't help in the least. I'd definitely stick to one with a throat latch, especially for trail riding.
I ride in a one ear and I have never had any problem with it. I usually am trail riding. But I recently attached a tie-down on it and it still is fine.. the tie down is for my horse that likes to have his head set way too high