1. Pricing Structure: In terms of pricing, Mailgun offers a pay-as-you-go model, where you only pay for the number of emails you send. They also have pricing tiers that offer additional features and support. On the other hand, Mailjet offers different pricing plans based on the number of contacts you have, with unlimited email sends included in all plans. They also offer additional features and support in higher-tier plans.

2. Email Deliverability: Both Mailgun and Mailjet have good email deliverability rates, but Mailgun has a slight advantage in this area. Mailgun has a strong reputation for high deliverability, with built-in features like dedicated IP addresses and email analytics that help ensure emails reach the inbox. Mailjet also boasts good deliverability rates, but it may not be as high as Mailgun's.

3. Ease of Use: Mailjet is known for its user-friendly interface and ease of use. The platform is designed to be intuitive and easy to navigate, making it a great choice for beginners or users who may not have technical expertise. Mailgun, on the other hand, has a more technical focus and may require some coding knowledge to take full advantage of its features.

4. Email Marketing Features: When it comes to email marketing features, Mailjet offers a robust set of tools. They provide features like marketing automation, segmentation, and A/B testing, which can help businesses optimize their email campaigns. Mailgun, on the other hand, focuses more on email deliverability and transactional emails, making it a better choice for businesses that prioritize transactional email over marketing email campaigns.

5. Email Templates: Both Mailgun and Mailjet provide email templates that can be customized for different purposes. However, Mailgun has a larger library of pre-designed templates that can be easily modified to suit your needs. Mailjet also offers customizable templates but may not have as extensive a library as Mailgun.

6. API Documentation and Support: Mailgun has a well-documented API that provides developers with the tools they need to integrate Mailgun into their applications. They also offer extensive API and developer support, making it easier for developers to troubleshoot any issues. Mailjet also provides API documentation and support, but it may not be as comprehensive as Mailgun's.

In summary, Mailgun and Mailjet differ in their pricing structure, email deliverability rates, ease of use, email marketing features, email templates, and API documentation and support. Depending on your specific needs and priorities, one may be a better fit for your business than the other.