In Tibetan Buddhism, there are four major traditions: Nyingma, Sakya, Kagyu and Gelug.
From the point of view of practice, they are all Mahayanists following the unity of Sutrayana and Tantrayana on the basis of Hinayana. But they do not differ from the points of view of action or philosophy.
Their differences are due to the time of their coming to Tibet, the different lineage of Lamas who have introduced them, the different emphasis on the various aspects of practice and the terminologies by which their teachings are transmitted.
All four lead to Buddhahood. Therefore, it is absolutely wrong to say one is better than another, or to disparage any of them.
Source: His Holiness the 14th Dalai Lama