I was involved in the process, and Amplify was the one that I preferred. But all three finalists were much better than Benchmark (though that is a low bar). Amplify CKLA is much more rigorous than Benchmark, so the transition may be tough--but outcomes should be better after students/teacher adjust.
The older version of the curriculum is available for free online--I think Amplify has the newer version so not sure how these compare:
Grades K-3:
https://www.coreknowledge.org/language-arts/
Grades 4-5:
https://www.coreknowledge.org/language-arts/
I hope that ultimately MCPS will continue the Amplify CKLA curriculum for grades 6-8, presuming implementation goes well at the ES level, as StudySync also leaves lots to be desired.