Unlike the ribosome, which can make an arbitrary sequence of peptides, an NRPS can only make one peptide sequence, although as a class, NRPS can make a wider diversity of peptides than can ribosomes.
Unlike the ribosome, which is fed an mRNA code and can make an arbitrary sequence of peptides, an NRPS does not accept a code and is preset to make one peptide. As a class, NRPS can make a wider diversity of peptides than can ribosomes.