1. Plugin Ecosystem: One significant difference between Grunt and Jenkins lies in their plugin ecosystems. Grunt has a vast collection of plugins available, covering various task requirements for JavaScript development and front-end workflows. On the other hand, Jenkins offers a wide range of plugins focused on automating and orchestrating continuous integration and delivery pipelines. This difference in plugin ecosystems reflects the contrasting focus and scope of the two tools.

2. Build Execution: Grunt is primarily used for task automation during the building of web applications. It simplifies repetitive tasks like minification, concatenation, and testing, making it an ideal choice for front-end developers. Jenkins, on the other hand, is a popular continuous integration tool designed to automate the build execution and integration process. It provides a platform for building, testing, and deploying software projects across multiple stages, making it highly suitable for larger development teams.

3. Scripting Language: Grunt uses JavaScript as its scripting language, making it easy for developers already familiar with the language to configure and customize tasks. Its configuration is based on a Gruntfile.js, allowing developers to define a list of tasks and associated configurations. On the contrary, Jenkins uses a domain-specific language (DSL) called Groovy to script its build processes. This difference in scripting languages may influence the choice of tool based on the developer's preference or existing skillset.

4. Architecture: Grunt follows a local-centric architecture where it runs directly on the developer's machine. This local execution enables developers to have more control and visibility over the tasks being performed. Jenkins, in contrast, is a server-centric tool that requires a dedicated server for its operation. It provides a centralized platform for managing builds, scheduling jobs, and distributing workload across multiple worker nodes.

5. Notification and Reporting: Grunt focuses on providing developers with immediate feedback during the development process through the command line interface. It lacks built-in reporting capabilities, and developers need to rely on additional plugins for generating reports. Jenkins, on the other hand, offers a comprehensive reporting and notification system. It provides dashboards, email notifications, and detailed build reports, allowing project stakeholders to monitor and track the progress of builds and tests effectively.

6. Community and Usage: Grunt has been widely adopted by front-end developers and the JavaScript community due to its simplicity and ease of use. It is commonly used for building and packaging JavaScript-based web applications. Jenkins, being a powerful and extensible tool, is widely utilized in enterprise environments where complex build workflows and integration processes are required. It is favored by DevOps teams and organizations implementing continuous integration and delivery practices.

In summary, Grunt and Jenkins differ in terms of their plugin ecosystems, build execution focus, scripting languages, architecture, notification/reporting capabilities, and target user communities. While Grunt is more suitable for front-end web development automation, Jenkins serves as a comprehensive continuous integration and delivery automation tool for larger software projects.