Have to agree with Aly on this one. My first concern is always that people will use prong collars incorrectly. I also believe that even though prong collars can be effective to some degree - current studies have proven that positive reinforcement has longer lasting effects than negative reinforcement (which a prong collar is). Gentle Leaders on the other hand are more about getting your dog to focus on you rather than what is two blocks ahead.

I also believe that any collar should be used as a tool only to aid training the desired behaviour. I used the Gentle Leader on Leo to help train walking nicely on a leash - I still used commands and treats and a clicker to reinforce the desired behaviour.

If you do use a prong collar (your choice obviously), it should be fitted and demonstrated by a professional trainer. JMHO