As in the case of synoptic parallels between the gospels, the main purpose of synoptic comparisons of rabbinic texts is to determine which elements are shared and which are different. The differences may either be features of the different pre-redactional versions, or they may be editorial. They are likely to be editorial if they fit – or even replicate – the subject matter, formulation, structure, ideology of the surrounding context into which the tradition was integrated. If there is no neat transition between the tradition and its context, that is, if there is no shared formulation and the purpose and theme of the tradition seem to differ from the context, editorial changes cannot be detected.
Catherine Hezser, “Form-Criticism of Rabbinic Literature”, in The New Testament and Rabbinic Literature, eds. Reimund Bieringer, Florentino García Martinez, Dider Pollefeyt and Peter J. Tomson (Leiden & Boston: Brill, 2010), 105.