I would personally recommend, if that's your thing, to look into "clean" Android devices such as Fairphones. Once the bootloader is unlocked, it's really trivial to install a decent Android distro without spyware, like /e/OS. I used to recommend LineageOS but it seems like it phones home by default these days: /e/OS is a Lineage fork without the spyware/telemetry.
Of course the best solution if you're not afraid to get your hands dirty is to compile Replicant Android from sources, but from what i heard it can be troublesome, and it's quite possible that blobfree Android does not fit your feature/usability expectations (eg. no GPS/camera/wifi), in which case a blobbed Android without OS-level spyware may be a good compromise.
I personally never had much faith in Apple (although i was a big fan of older MacOS UX), but these latest developments have completely broken any expectations i had from them:
- Apple Disables FaceID if you change the screen yourself [video] : https://news.ycombinator.com/item?id=28666836
- Old iPhones become faster if you change the region to France https://news.ycombinator.com/item?id=28291768
- macOS unable to open any non-Apple application https://news.ycombinator.com/item?id=25074959
There was also this comparative study of iOS/Android telemetry: https://www.scss.tcd.ie/doug.leith/apple_google.pdf
It concludes:
> We find that even when minimally configured and the handset is idle both iOS and Google Android share data with Apple/Google on average every 4.5 mins. The phone IMEI, hardware serial number, SIM serial number and IMSI, handset phone number etc are shared with Apple and Google. Both iOS and Google Android transmit telemetry, despite the user explicitly opting out of this. When a SIM is inserted both iOS and Google Android send details to Apple/Google. iOS sends the MAC addresses of nearby devices, e.g. other handsets and the home gateway, to Apple together with their GPS location. Currently there are few, if any, realistic options for preventing this data sharing.