Modern management or Windows 11? It’s more about "and" than "or"

Whatever works for you really. Using GP Analytics (which is built into Intune) is a good choice for initial analysis and possible migration, however, in general, we recommend that you take a step back and define your actual policy requirements as what you have captured in your current set of group policies is not necessarily a reflection of your requirements but is instead the culmination of a bunch of different opinions on configuration that have piled up over the last 10-20 years. Stepping back to your requirements and rationalizing your current policies so that you can implement only what you truly need is what we recommend orgs do as this embraces the entire point of moving to cloud-native which is simplification of management. Cloud-native management should be approach with what the mindset of what you should do and manage and not what you can do or manage. This will lead to the best path for success in both the short term as well as the long term.