When looking at a horse to see its conformation you want to break it down into sections. Legs, neck, back, etc. Each section has it's perfect confirmation and from there they can each have several flaws. I would start with that link in one of the first posts to research confirmation. There's a lot of good information there.
Again, the reason that confirmation is important is because of several reasons. Think of a person that is overweight let's say, they obviously can't do as much as an olympic runner. Also, not every person could be an olympic runner. So looking at that in the horse world, a perfectly conformed horse will be able to take you for a longer ride, jump higher, ride smoother, be more athletic, and the list goes on and on.
Great pictures, it does help to see it side by side. So what I see in the chestnut is being clearly downhill, a lack of neck, and long toes. Am I missing something? I read people making comments about weak loins, steep shoulders, something about the croup, is any of that going on?