1. Structure vs Formatting: JSON is a data interchange format used for storing and transferring structured data, while Markdown is a lightweight markup language used for formatting plain text documents. JSON focuses on representing data in a structured manner, whereas Markdown focuses on enhancing the readability and presentation of text.

2. Data vs Text: JSON is primarily used for representing and manipulating data, often in the form of objects and arrays. It allows for complex data structures, such as nested objects and arrays, and supports key-value pairs. On the other hand, Markdown is designed for writing and formatting text, providing simple syntax for making the text bold, italic, adding headers, links, etc.

3. Programmatically Processable vs Human-readable: JSON is designed to be easily parsed and processed by machines, making it an ideal format for transmitting data between a server and a client. It is often used with programming languages and APIs. Markdown, on the other hand, is intended to be readable by humans, allowing for easy editing and collaboration. It is commonly used for writing documentation, blog posts, and other textual content.

4. Extensibility vs Simplicity: JSON is extensible, meaning users can define and create custom data structures and add additional properties to objects. It provides flexibility in representing complex data types. Markdown, on the other hand, follows a simple and fixed set of formatting rules. While it offers some extensions like tables and task lists, it lacks the extensibility and versatility of JSON.

5. Strict Syntax vs Loose Syntax: JSON has a strict syntax that requires properly quoted keys and values, as well as correct placement of commas and brackets. It follows a specific set of rules and allows no room for error. Markdown, on the other hand, has a more forgiving and loose syntax. It allows for flexibility in terms of white spaces, line breaks, and formatting, making it easier to write and read.

6. Data Validation vs Raw Text: JSON supports data validation through various schema languages like JSON Schema. It allows users to define rules and constraints for validating the structure and content of JSON data. Markdown, however, does not have built-in capabilities for data validation. It primarily focuses on the presentation of text and does not provide mechanisms for enforcing data correctness.

In summary, JSON is used for structured data representation and transfer, suitable for machine processing and data validation, while Markdown is a lightweight markup language for text formatting, focusing on human readability and simple syntax.