1. Implementation: ImageMagick is a command-line tool that allows image processing and manipulation, while scikit-image is a Python library that provides various image processing algorithms as functions.
2. Programming Language: ImageMagick is not tied to a specific programming language, making it more versatile for different environments, whereas scikit-image is designed specifically for Python, making it easier to integrate with other data analysis libraries in the Python ecosystem.
3. Community Support: ImageMagick has a larger community base and has been around for a longer period, providing extensive documentation and resources, while scikit-image, although popular, has a smaller community compared to ImageMagick.
4. Ease of Use: ImageMagick focuses on providing quick and simple image processing tools through command-line interfaces, while scikit-image provides a more comprehensive set of algorithms for in-depth image analysis and manipulation.
5. Performance: ImageMagick is known for its speed and efficiency in handling large batches of images, making it ideal for batch processing tasks, whereas scikit-image may be slower in processing large sets of images due to its Python environment.
6. Flexibility: ImageMagick offers a wide range of image file format support and can work with various image types easily, while scikit-image may have limitations in working with some specific file formats or specialized image processing tasks.

In Summary, the key differences between ImageMagick and scikit-image lie in their implementation, programming language support, community backing, ease of use, performance, and flexibility.