Amazon. Apple’s system doesn’t use much of your bandwidth or have anyone else’s data going through your device (it’s completely anonymous).
I am not sure I understand why one is a concern while the other isn’t.
Find My identifiers have a single purpose, are useless to anything but the owners device, cannot be used by Apple for tracking, ads or whatever, and id be surprised if the entire payload after a day out is > 8KB total. These look completely different to me.
s/Amazon/Apple and you've got yourself the Airtag protocol. Obviously Airtags use less bandwidth, but both are proprietary and about equally as evil in my eyes.