1. Architecture: Datadog uses a centralized architecture where all data is collected and processed centrally. Sensu, on the other hand, utilizes a distributed architecture that allows for more flexibility and scalability in larger environments.
2. Monitoring Approach: Datadog focuses on metrics and logs for monitoring, providing a comprehensive view of system performance. Sensu, however, is more focused on event monitoring, allowing for more granular control over alerts and notifications.
3. Integration options: Datadog offers a wide range of integrations with third-party tools and services out of the box, making it easier to set up monitoring for various components. Sensu, while versatile, may require more customization and setup to integrate with specific tools.
4. Community Support: Datadog has a large user community and extensive documentation, making it easier to find solutions to common issues and share best practices. Sensu, although it has an active community, may not have as extensive resources available compared to Datadog.
5. Pricing Model: Datadog typically charges based on the number of hosts or instances being monitored, which can be more cost-effective for smaller environments. Sensu's pricing model may be more suitable for larger, complex environments with fluctuating monitoring needs.
6. Scalability: Datadog is known for its ease of scalability, allowing organizations to add more resources without much hassle. Sensu, while scalable, may require more manual intervention and configuration to handle large-scale monitoring needs.

In Summary, when comparing Datadog and Sensu, key differences lie in their architecture, monitoring approach, integration options, community support, pricing model, and scalability.