Falcon Proton is fully interoperable with OpenPGP (also maintains OpenPGP.js), Tuta does not.
Which is an attack vector and decrease in security.
Falcon Both providers must comply with the court's orders and provide the information they have about the user. This is only metadata because the email content is encrypted at rest. However, there is a difference:
Proton has more data to give as they don't encrypt the subject line and don't have perfect forward security.
Falcon German law can order Tuta to monitor the account and obtain the content before encryption (emails that will arrive "tomorrow" will be in plain text).
As far as I know, Swiss law cannot mandate this.
Both Tuta and Proton have been ordered to monitor suspicious accounts into the future and of course you can expect a company to not close business to protect your 10$ subscription privacy when the government knocks on the door. Don't trust anyone but yourself to protect your data.
All that being said (and I could name many disadvantages of Tuta here as well) neither of the two are good for your privacy, as E-Mail is incredibly flawed and should be avoided whenever better alternatives (such as Signal messenger) are available. But since most of us probably need a Mail address for certain actions, both providers are currently among the best available options. I use both for compartmentalization, and I see both have their advantages compared to each other.