The effects of both proton and neutron nuclear data libraries on the neutron field produced in light targets and transported through shielding material were assessed. The general-purpose nuclear data libraries JENDL-4.0/HE, TENDL-2017, ENDF/B-VII.0, ENDF/B-VII.1, ENDF/B-VIII.0, JEFF-3.1.2, and JEFF-3.3 were benchmarked using the MCNP6.2 Monte Carlo transport code. Three experiments from the SINBAD database, namely, 52-MeV protons hitting a carbon target and 43- and 68-MeV protons hitting a 7Li target, were selected for benchmarking. This selection was made according to their relevance for the MYRRHA accelerator-driven system to support the design of beam dumps and shielding of the 100-MeV section of the MYRRHA accelerator. It is demonstrated that the prevailing factor determining the transmitted neutron spectrum shape is the proton library from which the secondary neutrons are sampled. The choice of neutron library applied for the secondary neutron transport in the carbon and lithium targets, concrete and iron shielding, is of second-order significance.