Technically speaking is highly contested and you have arguments pro and con, one way an another. They use different technologies so it is hard to compare properly, specially since it depends on the users using it properly.

If the technology is good, it does not matter where it is located. Switzerland, specially since a couple of years, does provide more freedom guarantees than Germany but it is not immune at all, actually, the US had used the Alpine country to do operations due to its attractiveness to dissidents and criminals alike. However, for the overwhelming majority of customers, either option is fine for they privacy and security. Only metadata has been obtained in few instances in both companies and nothing else… at least no that was used in a court of law.

For ultimate targets, if they have to rely on email, that they should not, I would choose Tuta though. These are my reasons.

1. It has a lesser footprint, so less likely intelligence agencies tried to infiltrate it.
2. The people behind are there fro the very beginning and show their faces publicly (Many in Proton too like the CEO, but it is no so transparent with the rest)
3. The people of Tuta are more ideological so it is a barrier for intelligent services to penetrate. Tuta has show however being anti the Russian government (rightly or not), so this point is not valid if you are in that side.
4. Tuta has a very organic and progressive growth. Proton had an explosive growth. Of course, it could been good marketing, but still…
5. Proton still today requires Google’s Push Notification servers, after years and years demanding a solution. Tuta had that solved since long, long ago.
6. Recently a case came in Canada of a intelligent agent using Tuta since “it was infiltrate by intelligence agencies”… After a few hours going through the case, I read it the opposite, he used it because he actually considered it a better choice to cover his crime. He was not that high in the ranks, but I read that the he resumption o these officers.
7. Nothing regarding security, but as a paying customer for both I was “tricked” far less by Tuta. Proton, for instance, does not refund you, only gives you credits. Even 20min after an accidental 2yr renewal I got stuck with them unwillingly. That practice should never be acceptable for a SaaS.

Now, Proton overall, for most is a bit more reliable and full feature and better put together so it is easier to recommend. Think of Proton as the Apple of emails, quite secure and miles away from Gmail, but security wise and ethically, of the two, my bet would be with Tuta.