It's a benefit if for no other reason than choice is good. CFS may be the best "general purpose" scheduler, but that doesn't necessarily make it ideal for all workloads.
Similarly, "TCP Reno" and "TCP Vegas" (and now "TCP BIC") are good general purpose congestion control algorithms, but I have a server that I want to have very low network priority so I set it to "TCP LP" and I have another server that primarily hits wireless clients so I have that set to "TCP Westwood".
The ability to have a pluggable anything is a benefit because it can make hard things easy (if someone else already did the work) or at least possible because there's an infrastructure to tailor it to your individual needs.
Choice is good
It's a benefit if for no other reason than choice is good. CFS may be the best "general purpose" scheduler, but that doesn't necessarily make it ideal for all workloads.
Similarly, "TCP Reno" and "TCP Vegas" (and now "TCP BIC") are good general purpose congestion control algorithms, but I have a server that I want to have very low network priority so I set it to "TCP LP" and I have another server that primarily hits wireless clients so I have that set to "TCP Westwood".
The ability to have a pluggable anything is a benefit because it can make hard things easy (if someone else already did the work) or at least possible because there's an infrastructure to tailor it to your individual needs.