I personally have a lot of respect for Michael Ellis. He's a "balanced" trainer who - by everything I've seen by and about him - truly deserves that title; if corrections are inappropriate for a situation or the dog in question, he will say so and will not use corrections. It is not how I, personally, choose to train my dogs. I would only use corrections in training if it's a life or death situations AND corrections are appropriate for the issue (IE poisonous snake avoidance training), with the help of an experienced trainer with excellent timing to help, because I don't have the skills or confidence to do that myself. But I can respect a man who can adjust his training to the dog in front of him to keep training fun and engaging, and he is very successful at what he does. Afraid I don't have any solid sources on that one - this is an opinion I've developed over years of hearing bits and pieces from various sources (often forum posts like these!).
Ed Frawley is... good at what he does, in the sense of training IPO dogs. My issue is that he has a very, VERY poor understanding of force-free training, as seen here in an article written by Frawley himself:
http://leerburg.com/philosophy.htm. The relevant quote:
It totally misunderstands how rewards-based training works, and completely ignores the hundreds of thousands of people who have successfully trained service dogs, working dogs, sports dogs, companion animals, or (gasp!) have even rehabilitated aggressive or fearful animals without using any positive punishment. Apparently most of the dogs here are on the road to being sent to the pound for being horrid, unruly, 'dominant' (I'll get to what's wrong with this term in a minute) dogs, and if we just disciplined 'em a little harder they'd be perfect.
Victoria Stilwell... is a TV personality, and perfectly decent at what she does. She
generally advocates positive, force-free methods that aren't going to cause harm or make behavior worse if they're imitated by people watching at home. She's dramatic with the people, but hey, you have to make TV interesting somehow (especially when you're not goading dogs into reacting like some shiny-toothed celebrities). I don't think she's the best trainer out there, and I don't agree with everything she's said, but she's not the worse either. Again, this is mostly opinion based on my own viewing of the show and my own understanding of R+ training and dog behavior.
I know you didn't keep him on the list, but... please, PLEASE read this article:
http://www.whyanimalsdothething.com/posts/2016/6/2/the-damage-of-dog-whispering
I cannot bring myself to say much of anything good about Cesar Millan's training. He's done an enormous amount of damage to the public's views of dog training and behavior by dragging the outdated, utterly incorrect concept of dog-human dominance into the limelight (it was based on studies done in the 30s and 40s on a single population of unrelated wolves confined in a small enclosure; the scientific community now knows this is not how
wolves naturally act, let alone dogs, let alone how dogs interact with humans). His techniques are more than "not nice" - they're abusive and are actually very good ways to create and worsen aggression in many dogs. For everything he gets right (and 'dogs react to their handler's emotional state' is pretty basic stuff), he gets a lot more wrong, and it lands a lot of dogs in trouble because of how visible and imitable he is. If you have more questions about dominance or Cesar specifically, I'll be happy to dig up more on him! But you can also check out the references on that article I listed; the author has cited a lot of easily-accessible sources that are interesting reads in and of themselves.