I bought a Pixel just for GrapheneOS. Can't speak for anyone else.
> What features are those
There's a rather exhaustive list here:
https://grapheneos.org/faq#future-devices
Some that stand out to me:
> Hardware memory tagging
> Isolated radios (cellular, Wi-Fi, Bluetooth, NFC, etc.), GPU, SSD, media encode / decode, image processor and other components
> Weaver disk encryption key derivation throttling provided by secure element
Sounds like that's a feature in any ARMv9 processor, which would include current Xperias?
What you've linked is a long list but a lot of the items in it are underspecified and hard to search for. Would be good to be able to know what all these features actually do and why they do or don't exist in other models.
https://googleprojectzero.blogspot.com/2023/11/first-handset...