I use Parelli. I only had lessons (on horseback, never any ground work lessons) and when I got my horse, I wanted to start on the right foot.
I find that Parelli is easy to understand and I feel that my horse and I have a better connection/relationship because of it. I did not try any other methods because I tried Parelli first and since it's working, i'm sticking with it.
Even though they do push their products and they are expensive, I feel that are worth every penny,and I feel they help you to communicate better with the horse because of how they are designed. Though everyone has their own opinions :)
I know Parelli has a free DVD you can get off his website. I would also suggest seeing if the others have free DVDs. Also check out your library to see if they have any videos by them too.