@RANT you've got 3 options: FMC, FDM (local) or CDO (cloud). Ideally you'd use the FMC to manage the firewall, as it supports more features than if using FDM or CDO. It depends on exactly what features you require from the solution.
For anything other than the most basic features FMC will serve you better. You get a single place to manage the devices from, consolidated and historical reporting, management of a single set of objects, access to many more advanced settings etc.
You also now (as of July 2022) have the option of cloud-delivered FMC (cdFMC) built into CDO.
The few customers I have who went with FDM only are unhappy with their decision. One even switched to FMC later at considerable effort.