I know that I learn best from someone who will actually SAY something to me to help correct it as well as SHOW, but that is because I tend to be more able to learn via explanation than visually. That said, I have had the experience of training on a day to day basis under the instruction of a 5th (now 6th) Dan, who took the traditional Japanese approach. I didn't think I was learning much, as he rarely corrected me; but in retrospect, I see that I really learned a tremendous amount from him, most likely because of that approach. Now I get instruction from a very young 4th Dan, who corrects me both verbally and visually, and corrects me on a lot of subtle movements, and I find this amazingly helpful. I also find that I learn a great deal from folks at other dojos that I go to visit who give me little nuggets to take home.
Don't forget the beginners (and everyone else for that matter) too, because they teach you a lot if you are willing to listen to their bodies (but that is not what the thread was asking, so it is just an aside). We learn from everyone on the mat.
Maybe the rank thing has to do with where each of us is in our own training. I think as a teacher, the folks who most benefit from me are the early kyu ranks, as I am very good at showing basics and centering, whereas I am not at a stage in my teaching that I am particularly good with the fine subtleties. So, maybe a nidan/sandan is best for the lower kyu ranks, and a higher ranking teacher with umpteen years of experience is better for the higher kyu ranks and dan grades?
just my $.02