Powder bed fusion of polymers (PBF-P) is a powder- and beam based additive manufacturing technology for highly complex structures and demanding mechanical properties. Glass fiber filled systems allow for a higher stiffness or strength in additive manufacturing compared to neat materials. Fillers with a high aspect ratio change the process behavior regarding powder flowability as well as thermal and optical properties. While for the powder bulk good and processing rather short fibers are favoured, a critical fiber length has to be reached to obtain a strengthening effect for improving the mechanical properties. Therefore, a trade-off between processibility and mechanics has to be found. In this study, two different fiber length distributions and their effect on the powder, process behavior and mechanical properties are analysed and based on that recommended actions are given.