I believe that we are living in a world of economy! If we say that the “minor” Upanishads are profound, then you will agree, I hope, with those that feel that the “major” Upanishads are more profound.
The thing is ... in India, many great scholars accept sixteen or eighteen Upanishads as authentic and original. Some accept only twelve which they take as “major” and others accept only eight; the rest they consider “minor.” These people feel that not all but some of the Upanishads are momentous in their depths and in their embodiment of Truth. But you yourself will be the best judge. You kindly read the major ones first. According to me, the most significant ones are: Katha, Isha, Kena, Prashna, Mundaka, Mandukya, Taittiriya, Aitareya, Chandogya, Brihadaranyaka, Svetasvatara and Kaivalya.
I am sure, Gauri, that you know that there are only one hundred eight Upanishads! If you have the time, patience, inspiration and aspiration to study all the one hundred eight Upanishads, then it is simply wonderful. But do not come and tell me that some of the later Upanishads are not only insignificant, but a mere repetition of the former significant ones. To be frank with you, I have just studied sixteen. They have given me what I sought and at the same time, what they stand for: lofty aspiration and mystical revelations.