I think the concept of 'best trainer' is foreign to most of the nationally ranked instructors I have dealt with, I have heard too many of them encourage students to take as much training as they can manage from as many different sources as possible and use the best of what they learn for themselves. Still there are 'short lists' for most of the disciplines, those have been pretty well covered on this thread.
I'd say the most valuable training I have had was the 'zero to three feet' stuff from southnarc. Folks tend to think all they have to do is carry a gun and they'll be OK, that unfortunately isn't necessarily so. S'narc trains you for the up close and dangerous stuff, for 'when your awareness fails' as he puts it. I think enough of his methodologies to have arranged a private session with him for two of my teenage neices, neither of them can carry yet but the material he teaches on the victim selection process and contact distance self defence is worth their learning.
lpl/nc