1. Integration Capabilities: Graylog is primarily focused on log management, aggregation, and analysis, while Rollbar specializes in tracking real-time application errors and monitoring code changes. Graylog offers extensive integration capabilities with various tools and services for log management, including Elasticsearch, MongoDB, and Kafka, while Rollbar integrates with popular developer tools such as Github, Jira, and Slack.

2. Alerting Mechanisms: Graylog provides powerful alerting mechanisms based on logs and metrics, allowing users to set up notifications for specific events or conditions. Rollbar, on the other hand, focuses on providing intelligent error grouping and notifications for application errors, offering advanced features like grouping similar errors and aggregating error instances to reduce noise and focus on critical issues.

3. User Interface Design: Graylog offers a customizable and user-friendly web interface for log management and analysis, with features like dashboards, search capabilities, and visualizations. In contrast, Rollbar provides a sleek and intuitive interface specifically designed for monitoring and tracking application errors, emphasizing error details, stack traces, and context information to debug and resolve issues efficiently.

4. Data Volume Handling: Graylog is suitable for handling large volumes of log data, providing scalability options like clustering and sharding for distributed log processing and storage. Rollbar, on the other hand, is optimized for tracking errors and monitoring applications in real-time, focusing on capturing critical error events and providing detailed insights into code-level issues without the need for extensive storage and processing capabilities.

5. Role-based Access Control: Graylog offers robust role-based access control mechanisms that allow administrators to define granular permissions for users and teams, ensuring secure access to sensitive log data and monitoring capabilities. Rollbar also provides access control features but primarily focuses on providing visibility into application errors and code changes, with limited customization options for user roles and permissions.

6. Community Support and Documentation: Graylog has a larger community base with extensive documentation, forums, and resources available for users to troubleshoot issues, share experiences, and learn best practices for log management. Rollbar, being more specialized in error tracking, offers focused support and documentation for resolving application errors and improving code quality within developer workflows.

In Summary, Graylog and Rollbar differ in their integration capabilities, alerting mechanisms, user interface design, data volume handling, role-based access control, and community support/documentation.