1. Syntax: JUnit is a framework specifically designed for testing Java code, while SpecFlow is a testing framework that utilizes the Gherkin syntax to write acceptance tests in a human-readable format.
2. Platform: JUnit is primarily used for unit testing in Java applications, while SpecFlow is geared towards behavior-driven testing and is commonly used in .NET applications.
3. Integration: JUnit integrates seamlessly with tools like Eclipse and Maven for continuous integration, while SpecFlow can integrate with a variety of automation tools such as Selenium and Appium.
4. Language: JUnit is solely based on the Java programming language, whereas SpecFlow supports multiple languages like C#, Java, and Ruby for writing test scenarios.
5. Reporting: JUnit provides detailed reports of test results in XML format, making it easier to analyze failures and errors, whereas SpecFlow offers customizable reports through plugins like ExtentReports or SpecRun.
6. Collaboration: SpecFlow promotes collaboration between business stakeholders and developers by using plain English specifications, fostering better communication and understanding of the testing process.

In Summary, the key differences between JUnit and SpecFlow lie in their syntax, platform, integration, supported languages, reporting capabilities, and focus on collaboration with stakeholders.