I think you are wise in not naming your teachers at this point. As long as you're still going through these very rigorous years of training and exams, where many teachers have to approve your work along the way etc... If you were older, I see SDL's very good point about the forum group benefitting from one another's experiences, but it seems that you're in a vulnerable position just now. Anyway, back to playing: I'm sympathetic to your dilemma here. Whom to trust??? I don't really have technical advice, since there are so many who play so much better than I do. A great many on this forum, I'm sure. But here's a theory: as a general sifting process, I think it's important to recognize that people who DO things well can't always explain how they do them. Forgetting for a moment all the blah-blah-blah from your teachers, are there any among them who just seem to PLAY naturally and easily themselves? Someone who plays a lot every day and never seems to get tired, who learns new pieces quickly, doesn't have to do a passage hundreds of times to figure out the technique for it... a good problem-solver in his or her own playing who seems strong but flexible while playing. There are people who just do things naturally well, or learned it well so long ago that they don't know how they know it. And then there are people who had to fight through barriers and really solve problems in order to do the thing well. Either one can be a good role model, but if you know which teacher is which, you might respond differently to their advice. The people who had problems initially can be great teachers because they had to learn solutions which they can teach you. The problem is, if their obstacles were different from yours, they might be giving the solution to their problem, not your own. The "naturals" and freakishly talented are great if you can figure out what they're actually DOING. The problem with them is they often don't know, so you have to be a detective, keep asking questions and keep watching. What they say might be the opposite of what they do (not on purpose, of course), and if they're great, you want to do what they do, not what they say. It's a sticky wicket, but you sound really smart. Best of luck...
Final thought, I still can't tell exactly what your teacher wants to hear in your "pure finger work," or what you think you should be able to do that you can't. You may have spelled it out and I forgot-- sorry. But Bernhard has written some fantastic things about practicing at tempo really early in a piece, to figure out physically how to manage hard passages in the most efficient way. Maybe I should have just started with that! I don't know how to tell you to find it, but someone will know. I must echo all the people encouraging using "real", beautiful music to work on technique. Life is short, there's a lot of great music out there that we won't even get to in our lifetimes. But we can try!