Which solution will meet these requirements with the LEAST operational overhead?

Explanations:

Amazon Macie is specifically designed for discovering and protecting PII and sensitive data in S3 buckets. Configuring it in each region allows for a tailored analysis of PII stored in us-east-1 and us-west-2 with minimal operational overhead. It automates the discovery process and provides detailed reports on PII findings.

AWS Security Hub aggregates security findings but does not specifically analyze data in S3 for PII. AWS Config rules can help monitor configurations and compliance, but they do not perform data analysis to discover PII. This option would require additional manual processes to identify PII, leading to higher operational overhead.

Amazon Inspector is primarily focused on security assessments for applications running on Amazon EC2 and other AWS services, not for analyzing data in S3. Therefore, it would not effectively identify or analyze PII in S3 buckets, making it an unsuitable choice for this requirement.

Amazon GuardDuty is a threat detection service that monitors for malicious activity and unauthorized behavior, but it does not specifically analyze S3 data for PII. While it may enhance security posture, it does not fulfill the requirement of discovering PII in S3 buckets, resulting in incorrect operational applicability for this scenario.