ProtonMail also encrypts emails, contacts, contents, attachments, of all emails you send and receive, with end-to-end encryption.
However, the most important differentiator is the trust model. ProtonMail has Address Verification, which means it is trust on first use, which is significantly more secure than the trust on every use model Tutanota uses for key distribution. Details here: https://www.reddit.com/r/ProtonMail/comments/b84kd3/why_is_p...