a) it's much easier to work with b) you have much more monitoring possibilities c) it adds a pile of features d) you can host all supporting services (sync, updates, telemetry, etc) on premise - if you want

The current policies are not very enterprise-friendly yet.

Some settings are flat out refused (for "security reasons"). And with each new update there are a few new popups / invitations to try this new feature / re-enabling the v2 of the thing of which the v1 was already opted out in the policy. And it seems like you cannot apply new policy while the browser is running - meaning it cannot be used to roll out hotfixes without interrupting the work of currently unaffected workstations.

And then there is the syncing. If you want to manage & sync history, bookmarks and the password managers content.. you are probably going to find that easier by overriding the builtin features with 3rd-party extensions, as the builtin sync feature is very much tailored to the needs of privately owned devices and one-device-at-a-time usage patterns.