Here is my opinion from what I have seen and experienced..
I have been to two Dennis Reis clinics..IMO, while I think he is obviously a great trainer- he's gotten so gimmicky.. The only useful thing I got out of his first clinic was foot fall and how it applies to properly cueing your horse. The rest of the day consisted of "look what my horse can do, yours can do it too..." if you want to drop $1500 on his training DVDS (wich will most likely end up on EBAY
for half price
I have also been to a Chris Cox clininc- Not gimmicky and Very informative!- at least he was this way when I went about 4 years ago. At the clinic he did a GREAT job of helping a few unconfidant ladies with their horses..
I like Clinton Andersons Method, but he has gotten so gimmicky as well that I only ever see him on rfd... and really if they have gotten to the point of " you can't TRAIN YOUR HORSE PROPERLY WITH OUT MY $60 ropehalter" I start staying clear.. I am contemplating buy his book, but that's where it will end!
I Love Craig Cameron, Had his book..it was very easy to understand and he doesnt blow smoke up your but about keeping a horse that is wayyy beyond your capabilities or goals. He is very honest and open. And he doesnt attempt to get you to buy useless pieces of equipment with his name on it..
As for anything parelli...ugh. I have has personal experiences with parelli trained horses and they tend to be PUSHY. He is sooo darn gimmicky (THE WORST)..I have seen old pre linda Videos and he no doubt is a good trainer (studied tom dorrance and ray hunt- he knows his stuff), but it all has gotten lost in the "games" and being your horses friend.. and don't even get me started on the way Linda parelli advocates you ride...when ever I see her on RFD..i just can't help but laugh at her absurdness.