Ecollar Technologies has come out with a vibration-only "pager" collar they are selling for $189.99. A lot of people seem to like it, but I am glad I have the regular stim collar for my two dogs. Each to his own, and I suspect this has more to do with human comfort and self-perception than anything else.
Most dogs want to obey, and do not need too much of a "tap" to help them work through their Attention Deficit Disorder issues. That said, there are times when a dog is very "amped" due to a fight-or-flight, or prey-drive situation. In those cases, I want to be able to "turn up the heat" so the dog can "see the light." It may not take much, but it may take more than a vibration that the dog has fully explored the limits of. To be clear, however, I have no experience with this "Pager Only" set up. Do you?