Parameter Store provides a bit more versatility. It has the option to store data unencrypted or to encrypt the data with a KMS key. With Secrets Manager, the secrets are stored encrypted and there’s no option to store unencrypted data. So that’s one use case for Parameter Store.

SSM Parameter StoreAWS Secrets Manager
Store values up to 4096 Characters4KB or 8KB64Kb
Values can be encrypted with KMSYesYes
Can be referenced in CloudFormationYesYes
Built-in password generatorYes
Automated secret rotationYes
Cross-account accessYes
Additional CostFreeĀ for standard parameters. Advanced parameters are charged per parameter and API transactionYes