GPGMail is a plugin for Apple Mail that focuses on PGP encryption and is best for users within the Apple ecosystem, while ProtonMail is a standalone email service that emphasizes privacy and security for all users, regardless of platform.
GPGMail
Pros:
End-to-end encryption
Seamless integration with Apple Mail
Supports PGP encryption
User-friendly interface
Open-source software
Cons:
Requires technical knowledge for setup
Limited to Apple ecosystem
May have compatibility issues with non-Apple mail clients