On the one hand, AWS Macie only scans S3. Google DLP API works on S3, Gmail, Drive, GCS, DynamoDB, Redshift, BigQuery, Slack, SQL, Oracle, Oracle RAC, Zendesk, Twilio, Salesforce, and everything you can point an API at. If you want to use the same engine to test all your repos then Google DLP API is the right solution for you.
On the other hand, Macie has a GUI wizard. DLP API is an API. So if you can't code and just want to scan S3 then Macie might be for you, until Google DLP builds a GUI, if there's demand for that.
Someone should do a comparison of how successful each engine is at picking up sensitive data. I suspect Google DLP will be tuned better, but someone should do the test on a dummy data set and release results. That would be the most interesting comparison.
On the other hand, Macie has a GUI wizard. DLP API is an API. So if you can't code and just want to scan S3 then Macie might be for you, until Google DLP builds a GUI, if there's demand for that.
Someone should do a comparison of how successful each engine is at picking up sensitive data. I suspect Google DLP will be tuned better, but someone should do the test on a dummy data set and release results. That would be the most interesting comparison.
I work for Google.