If you care about owners, Proton loses

I've been using Tuta for a while. It's had a few minor issues, but all fixed fairly quickly. No major issues.

I suspect Proton would be about as good. The main reason I didn't pick Proton was the owner's political position.

I've been using Proton for five or six years, but I'm seriously thinking about switching because they don't currently support Monero payments.

I used to be a Proton user (paid) for over a year, but I left them due to their lack of support/development of Linux programs.

I didn't go for Tuta as I could not use Thunderbird or any client of my choice, felt even more of a vendor lock-in than Proton.

Then, I shifted to mailbox.org and I manage my own PGP keys.

Your choice depends upon what exactly you need.