If you are managing PBN's which in this case many members in this forum do. Do you guys use a single registrar or use many registrar?
I myself don't prefer more than one registrar unless it is utmostly needed.
Services like Namesilo or namecheap provides all the resources and support to manage hundreds of domains at one single time. So, what else do you need?
For me a single registrar such as Namesilo is more than enough.