According to one view, mustafīḍ (مستفیض) is a narrower kind of mashhūr: besides meeting the mashhūr conditions, it has an equal number of narrators in every generation.
• Equal numbers: it is called mustafīḍ in this narrower use.
• Numbers vary: it remains mashhūr if the mashhūr conditions hold, but it is not mustafīḍ in this narrower use.
Under this view, mashhūr is broader and mustafīḍ is narrower.1
1. Broader and narrower: under this view, every mustafīḍ is mashhūr, but not every mashhūr is mustafīḍ.