There is no comparison between Crypto AG and us. Our encryption occurs client-side and our cryptographic code is open source and backed by third-party audits: https://proton.me/community/open-source
One thing that might put others at ease is having a way for client-side code to NOT be automatically updated, as some view this as a type of backdoor or method that malicious code might be injected without being noticed, even if unintentional.