It might have to do with e.g. Apple having rolled out MIE at a broader scale than Google rolling out MTE on PixelOS, where AFAIK it is still largely opt-in (not 100% sure, I always wipe a Pixel immediately).
That's impressive!!
iPhones are probably the most secure off the shelf phones you can buy, but based on leaked documents it's clearly inferior real-world security compared to a Pixel running GrapheneOS. Apple and Google have copied many security features from GrapheneOS like the reboot timer.
GrapheneOS is built from the ground up with a primary priority placed on security. GrapheneOS has much more robust USB port hardening. You can see the full list of features added on their website. Apple bolts on some additional security features in lockdown mode but they are mostly fixes to Apple's services which have large attack surface like iMessage. Additionally they are all built together and not on by default which makes the users willing to use it way lower.
Probably the latest models. Cop told me they have problems cracking those. Older models not so much, that's pretty common knowledge.
So then the best chance for security is to stay up to date with everything, including the latest HW model. At least this gives an attacker a window of only ~1 year to find and exploit a vulnerability.