Both are terrible for privacy so it comes down to which one has a nicer screen now. :(
I'd rather have Google check an Apple phone attestation than have Google check a Google phone attestation, and vice versa, though, because you can assume each company is trying to keep as much information private to themselves instead of giving it to the other. Google is probably just getting "yes it's an Apple phone" and some kind of temporary token, instead of my IMEI, IMSI, phone number, all signed in accounts, biometrics and so on.
I'd rather have Google check an Apple phone attestation than have Google check a Google phone attestation, and vice versa, though, because you can assume each company is trying to keep as much information private to themselves instead of giving it to the other. Google is probably just getting "yes it's an Apple phone" and some kind of temporary token, instead of my IMEI, IMSI, phone number, all signed in accounts, biometrics and so on.