I don’t want to see PGP rejection based on usability. So, to level the field at user level we take Delta Chat, which uses PGP. If I understand that correctly.
I have no knowledge of telegram security at all.
I’ve never seen anyone use Telegram’s e2ee. Not even by the users outside the legal realm, to put it mildly. Not only is it opt-in but it also works in the mobile app only.
I’ve used it, on Windows
So how do you start or join a secret chat on Windows?
Custom third-party clients. It’s a mess.
Telegram is not private. That makes the comparison to be infinity in favor of DeltaChat.
If you have to choose go for PGP. However, there are much better options
Whatever are those options?
Simplex Chat and other encrypted messagers
Regarding privacy, PGP is far better than out-of-the-shelf IM-embedded encryption, if used correctly. Alice uses Bob’s public key to send him a message, and he uses his private key to read it. He uses Alice’s public key to send her a message, and she uses her private key to read it. No one can eavesdrop, neither governments, nor corporations, nor crackers, no one except for Alice and Bob. I don’t get why someone would complain about “usability”, for me, it’s perfectly usable. Commercially available “E2EEs” (even Telegram’s) aren’t trustworthy, as the company can easily embed a third-party public key (owned by themselves) so they can read the supposedly “end-to-end encrypted” messages, like a “master key” for anyone’s mailboxes, just like PGP itself has the possibility to encipher the message to multiple recipients (e.g. if Alice needs to send a message to both Bob and Charlie, she uses both Bob’s and Charlie’s public keys; Bob can use his own private key (he won’t need Charlie’s private key) to read, while Charlie can use his own private key to do the same).