As the Wikipedia article indicates, Bloch’s definition of feudalism is broader than Ganshof’s and includes many social relationships, such as among family members, in addition to formal ties of vassalage among members of the nobility. According to Brian Tierney, Ganshof’s definition is still the more generally accepted one among professional historians.
I don’t have access to Susan Reynolds’s writing here; her Wikipedia page says she thinks “direct ownership of land was more prevalent in the early Middle Ages than has been thought, and the decline of central authority has been exaggerated.” I think you’d have to be a specialist to evaluate this claim because it involves interpreting nuances in manuscript documents from the period.
I hope this helps!
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