Telegram has, by design, message content accessible to whoever runs the servers. WhatsApp has gone to great lengths to not have that.
Obviously there’s client security, potential backdoors, unencrypted backups, and many other things to worry about. But I don’t see a scenario where it fares worse than Telegram, and many where it’s significantly better.
Whatsapp has to have some kind of escape hatch if not back door simply because of the amount of heat it doesn’t get (think of all the regimes who are ok with it).
I believe that escape hatch to be cloud backups, which are heavily encouraged by the UI and not end-to-end encrypted by default. iMessage has made the same compromise.
As long as enough people click that checkbox, law enforcement has access and Meta/Apple are out of the news without having lied about or hidden anything.
Obviously there’s client security, potential backdoors, unencrypted backups, and many other things to worry about. But I don’t see a scenario where it fares worse than Telegram, and many where it’s significantly better.