Portable judgment vs. platform mastery
The CISSP certifies senior security judgment independent of any product: how to govern risk, design architecture, and run security programs anywhere. Its value is portability; it reads the same to a bank, a hospital, and a startup.
The SC-100 certifies the ability to design end-to-end security solutions on Microsoft's platform: Zero Trust strategy with Entra, threat protection with Defender and Sentinel, data governance with Purview. Its value is depth, and that depth is denominated in one vendor's stack.