1. Workflow Integration: Board For GitHub mainly focuses on integrating GitHub issues and pull requests into a kanban board, making it easier for teams to manage and track their tasks. Gitboard, on the other hand, offers a more comprehensive project management solution by incorporating task lists, due dates, and file attachments to enhance team collaboration. ZenHub, though, takes it a step further by integrating directly into GitHub's interface, providing an extensive set of project management tools seamlessly within the platform.

2. Features and Capabilities: Board For GitHub offers a simple kanban board layout with basic task management features, while Gitboard provides more advanced task tracking capabilities such as task sorting, filtering, and custom tags. ZenHub, however, stands out with a variety of features like burndown charts, release planning, and automated workflow processes, making it a robust project management toolset for GitHub users.

3. Team Collaboration: Board For GitHub allows teams to collaborate on tasks within the GitHub interface easily, but Gitboard goes a step further by offering real-time collaboration features like comments and task assignments. In contrast, ZenHub enhances team collaboration with features like Slack integration, cross-repository linking, and multi-repo reporting, facilitating seamless communication and coordination among team members.

4. Customization Options: Board For GitHub provides basic customization options for kanban boards, while Gitboard offers more flexibility with customizable workflows, task types, and user permissions. ZenHub takes customization to the next level by allowing users to create custom reports, workflows, and automation rules tailored to specific project requirements, making it a highly adaptable project management tool.

5. Usability and Interface: Board For GitHub features a straightforward and user-friendly interface, making it easy for new users to get started quickly. Gitboard enhances user experience with a more intuitive design and interactive elements like drag-and-drop task management. ZenHub, with its seamless integration into GitHub's interface, provides a familiar user experience while offering a wide range of project management tools right at users' fingertips.

6. Scalability and Performance: Board For GitHub is suitable for small to medium-sized teams looking for a simple project management solution, while Gitboard caters to larger teams with more complex task tracking needs. ZenHub is designed to scale with enterprise-level organizations, offering advanced project management features and performance optimizations for large-scale projects with multiple repositories and cross-functional teams.

In Summary, the key differences between Board For GitHub, Gitboard, and ZenHub lie in their workflow integration, features and capabilities, team collaboration options, customization flexibility, usability, and scalability for different team sizes and project requirements.