Various borazine-based polymeric precursors can be prepared from tris(alkylamino)boranes and B-tri(chloro)borazine. Their chemical structures are described and compared in this review, along with their melt-spinnability. After polymer-to-ceramic conversion, the mechanical performances of the ensuing BN fibers are analyzed in relation with the structure of the corresponding thermoplastic polymers. The most promising results were obtained with B-tri(methylamino)borazine, which appears, at the present time, as the best candidate for a potential industrialization of the process. However, promising results were also obtained with borylborazines. This comparative study clearly emphasizes that the synthesis of tailored polyborazines is one of the key point for the preparation of high-performance BN fibers.