Amazon Simple Queue Service (SQS) enables the queuing of messages, which helps in decoupling the components of a system. For the trading company's need to buffer transaction orders and allow for delayed processing, SQS is a fitting choice as it can handle a high volume of messages and maintain them until the consuming service is ready to process. This ensures that the architecture can scale and that the individual components are loosely coupled. On the other hand, AWS Transfer Family is used primarily for secure file transfer and does not provide queuing capabilities. The AWS Secrets Manager is tailored for managing sensitive information, which is not relevant to the message queuing requirement. Amazon RDS is a database service and does not offer message queuing functionality.