1. Scalability: Azure Functions provides a serverless computing platform, which means it automatically scales up or down based on demand. RabbitMQ, on the other hand, is a message broker that facilitates communication between different systems. While Azure Functions can handle a large number of requests by scaling horizontally, RabbitMQ achieves scalability by distributing messages among multiple queues and consumers.

2. Event-driven architecture: Azure Functions is designed to respond to triggers and events, such as HTTP requests or changes in Azure services. It allows developers to write small, single-purpose functions that execute in response to these events. RabbitMQ, on the other hand, follows a publish-subscribe model where messages are sent to exchanges and then routed to different queues based on bindings. Consumers can subscribe to these queues and process the messages asynchronously.

3. Managed Service vs. Self-hosted: Azure Functions is a managed service provided by Microsoft, which means the infrastructure, patching, and scaling are all handled by Azure. On the contrary, RabbitMQ is a messaging middleware that needs to be deployed and managed by the users themselves. While Azure Functions abstracts away the underlying infrastructure, RabbitMQ requires setting up and maintaining the message broker infrastructure.

4. Protocol Support: Azure Functions supports a variety of protocols for triggering the functions, such as HTTP, timer, or Azure Storage events. It can also integrate with other Azure services through bindings. RabbitMQ primarily uses the Advanced Message Queuing Protocol (AMQP) for communication, which is a reliable and widely adopted messaging protocol. Additionally, RabbitMQ supports other protocols like MQTT and STOMP.

5. Function Runtime: Azure Functions runs on the .NET runtime, but it supports multiple programming languages like C#, JavaScript, PowerShell, Python, and Java. Developers can choose the language of their preference to write the functions. RabbitMQ, on the other hand, is a message broker that can be used with various programming languages as it follows the messaging patterns and protocols.

6. Deployment and Maintenance: Azure Functions can be easily deployed and managed through Azure portal, command-line tools, or CI/CD pipelines. The scalability and availability are automatically handled by Azure. On the other hand, RabbitMQ requires manual installation and configuration on servers or containers. It needs ongoing maintenance to ensure high availability, security, and performance.

In Summary, Azure Functions is a managed serverless computing platform with event-driven architecture, supporting multiple protocols and languages, while RabbitMQ is a self-hosted message broker that provides scalability, flexibility, and multiple language support for building distributed systems.