The benefit of Cedar mainly comes down to the language. Cedar was designed to sit in the middle of a runtime call, so it has reliably low latency (see comparison here: https://twitter.com/Sarah_Cecc/status/1766141060370329748) even at high scale. It's way more readable so it's easier to author and debug. And it's validated against formal methods proofs so certain properties of the language (like default deny) are mathematically proven. More about the benefits of Cedar here: https://cedarland.blog/design/why-cedar/content.html

AWS uses it and the policy language is similar, and if you are all in on AWS, then it makes sense to keep it for consistency?