In this day and age, and esp when I am still an active Facebook / WhatsApp / IG user, I really find it quite ironic that I am posting about personal data privacy concerns. But spurred by the upcoming user agreement changes from WhatsApp, I did a bit of homework and decided that I would at least remove the Facebook Messenger app from my phone, and follow Elon Musk's recommendation to use Signal over WhatsApp as much as possible.
Here is a quick comparative diagram of the persoal data that each messaging apps collect from you and your iOS device when you install / use the app. The number of data items each app collects from you is as follows:
Signal: 1 -- your phone number is collected, but it is not tied to your Signal account
Telegram: 4 items
iMessage: 4 items
WhatsApp: 32 items
Facebook Messenger: over 100 items
While the collection of private information here only applies to the iOS / Apple Store version of the app, I am willing to bet that a similar amount of data is collected on the Android version of the apps as well. The Google Play Store does not require this level of information to be declared, so it is difficult to tell how exactly the apps behave in an Android environment.
Getting back to the personal data collected on an iOS device, I have personally verified the truthfulness of this data privacy collection, and you can see for yourself the data items each app collect from your iOS device from the following links:
Signal:
https://apps.apple.com/.../signal-pr...../id874139669
Telegram:
https://apps.apple.com/ca/app/telegr...er/id686449807
iMessage:
https://support.apple.com/en-gb/HT211975
WhatsApp:
https://apps.apple.com/ca/app/whatsa...er/id310633997
Facebook Messenger:
https://apps.apple.com/ca/app/messenger/id454638411
Finally, if you are interested in the subject, the following two articles might be of interest to you:
WhatsApp Beaten By Apple’s New iMessage Privacy Update
Do You Suddenly Need To Stop Using WhatsApp?