Which is better, Tutanota or ProtonMail?

For the free versions, they are pretty similar, except ProtonMail supports PGP which works with people who don't use ProtonMail, whereas Tutanota uses its own encryption which only works with Tutanota users. Neither of them support third party clients (although ProtonMail has an IMAP bridge for desktop for their paid version), so I would say ProtonMail is better for that reason. Both of them are much better than Gmail though privacy-wise.

However, one thing to be careful of is that unlike Gmail, neither of them support email forwarding, which might become a problem if you want to switch email providers again. A workaround for that is to buy your own domain and use the paid version of whichever service you choose so you can change services without changing your email address. For that feature, Tutanota costs significantly less than ProtonMail does.

If you want an email provider that is more focused on features like Gmail but doesn't sell your data, you can also look at FastMail (Australia) or Mailbox.org (Germany). FastMail (what I use) has a better UI, but it is based in a country with anti-encryption laws. While ProtonMail/Tutanota are trying to be government proof by end-to-end encrypting your emails at the expense of features, FastMail/Mailbox.org are more focused on productivity without making money off of your data. To me, FastMail/Mailbox.org have good enough privacy since I use Signal for most personal communications I want private, but if a government is after you for some reason, ProtonMail/Tutanota would definitely be a better option.

I used both for a time. Ultimately, I felt protonmail provided the better experience with its cleaner interface and “bridge” client that let you use a program like thunderbird. It also had fewer ddos issues than tutanota, but it seems I was simply using tutanota at a rough time and those might not be as big a thing anymore.

All that said, I decided both platforms were somewhat without a point as no one else I knew used them. Which meant I may as well be using any other email platform out there. I settled on mailbox.org for my personal email. They are privacy respecting and work out of the box with any client I want. And I can still send encrypted email if I feel the need to do so.

I have been using ProtonMail for more about a year and never faced any issue. Never used Tutanota.

Both are pinned to my Vivaldi as we speak... converse. Proton Mail has some extra features (vpn), and I like it's interface a little better, but I've been using Tutanota for much longer. Tutanota has had some issues with the German government I believe, but as far as user security I have never had an issue with Tutanota - though they did have a strange string of ddos attacks a couple years back if I remember correctly.