1. Integration with existing systems: Userbin is designed to be seamlessly integrated with existing authentication systems, offering a smooth transition for users. Oso, on the other hand, focuses more on authorization policies and can be integrated into existing applications without the need for major changes.

2. Focus on authentication vs authorization: Userbin primarily focuses on authentication, providing secure login and user management functionalities. In contrast, oso is tailored to handle complex authorization logic, allowing developers to define policies for controlling access to resources within their application.

3. Fine-grained access control: Oso is known for its fine-grained access control capabilities, enabling developers to define granular policies for determining what actions users are allowed to perform. Userbin, while secure, may offer more limited options in terms of fine-tuning access control.

4. Community support and documentation: Userbin boasts a strong community base and extensive documentation, making it easier for developers to troubleshoot issues and find resources for implementation. Oso, although gaining popularity, may have a slightly smaller community presence and documentation coverage.

5. Scalability and performance: Userbin focuses on providing a scalable solution with optimized performance for authentication needs. Oso, while not sacrificing scalability, places a higher emphasis on the flexibility in defining complex authorization rules, which could impact performance in certain scenarios.

6. Licensing and cost: Userbin's licensing model may differ from oso's, potentially affecting the overall cost of implementing either solution. It is important to review the licensing terms and associated costs to determine the best fit for the project's budget and requirements.

In Summary, Userbin and oso differ in their focus on integration, authentication, authorization, access control, community support, scalability, performance, licensing, and cost considerations.