1. Data Collection: AppDynamics collects data through the use of agents embedded within the application servers, providing detailed insights into application performance metrics, user experience, and business transactions. In contrast, StatsD is a lightweight network daemon that collects and aggregates custom application metrics, allowing for more flexibility in the types of data that can be monitored.

2. Monitoring Approach: AppDynamics offers end-to-end monitoring of applications, servers, and databases, providing a comprehensive view of the entire IT environment. On the other hand, StatsD focuses primarily on monitoring custom application metrics and does not offer the same level of depth and breadth as AppDynamics in terms of infrastructure monitoring.

3. Alerting Capabilities: AppDynamics includes robust alerting capabilities, allowing users to set up customizable alerts based on predefined thresholds for different metrics. In comparison, StatsD does not have built-in alerting features and often requires integration with additional tools or services to set up monitoring alerts.

4. Scalability: AppDynamics is designed to scale with enterprise-level applications, offering support for large-scale deployments and complex IT environments. StatsD, on the other hand, may struggle to scale effectively in high-traffic or highly distributed application environments due to its lightweight design.

5. Granularity of Data: AppDynamics provides granular visibility into individual transactions, method calls, and database queries, enabling in-depth performance analysis and troubleshooting. In contrast, StatsD typically aggregates metrics at a higher level, offering a broader overview of application performance but with less detailed information.

6. Integration Capabilities: AppDynamics offers out-of-the-box integrations with a wide range of third-party tools and services, facilitating seamless integration into existing IT ecosystems. StatsD, while extensible through plugins, may require more manual configuration and maintenance to integrate with other monitoring or analytics platforms.

In Summary, AppDynamics excels in providing detailed end-to-end monitoring and alerting capabilities for complex enterprise applications, while StatsD offers lightweight and flexible data collection for custom metrics monitoring with less scalability and integration options.