The Ribhu Gita and other Advaita Gitas seems stuck at the unity state, while Robert and Nisargadatta talked about that which is entirely beyond that. Robert never understood my Zen no-mind states where the emptiness ate me and I saw the world as me in complete, physiological, no-separation.
So pick the teacher closest to your heart; you will have his or her sort of experiences. The teacher's experiences and methods will lead you to a whole class of "spiritual" experiences. Zen Buddhism has different experiences and understanding from Tantric and Theravadin Buddhism. Advaita is different from Buddhism in many ways, just as they share commonalities.
Then after completing a relationship with your teacher, you may feel it is not enough. Buddha accepted teachings from many sages and rejected them all. They did not satisfy him, or answer his most heart-felt questions. So he struck out on his own and invented Buddhism, which over 2,500 years created a hundred schools of philosophy and spiritual practices, including self-inquiry.
The teacher deeply affects the course of your experiences and your understanding and interpretation of those experiences. That is why you need to choose a teacher who has integrity and has really attained some release through his teacher.
U.G. Krishnamurti knocked Jiddha Krishnamurti's teachings, but spent years around him and had a J. Krishnamurti experience on steroids, rather than a Ramana Maharshi experience, a man who also influenced him.
Each teacher is like the end of a line of spiritual experiences, a flowering. Sometimes they think their experiences are the highest, a claim which becomes even more inflated by adulating students.
Which is greatest tradition and teacher? I guess whichever one gives you rest and completion, and I don't mean just by saying, "Whatever." You follow a teacher or lineage until you find completion, satisfaction, and there is no room for other teachings at that point, or you embrace them all as valid songs of Consciousness, Gitas revealing some aspect of Consciousness' forms.
My way is kind of an amalgam of Zen, traditional Advaita, via Robert Adams and Nisargadatta, and Bhakti, Love. I see meditation, self-inquiry, ecstatic surrender, and compassion in action as all leading to freedom. But that is me. I make no claim that all the nonsense I teach is the highest or best. What I say, is just words, and none touch reality. It really helps to become dumb as a rock and just look within, fill yourself with your own presence, love that presence, and go beyond.
You just have to come and sit with me to know my way.