Pixels have many hardware security features that can’t be found on any other Android phone. Examples are the Titan M2 chip, which uses the Android StrongBox and Weaver API, Insider Attack Resistance and hardware attestation. It enables a strong implementation of Android Verified Boot. On many other Android devices, Verified boot is insecure or entirely broken. Pixels are also the only phones on the market with hardware memory tagging.

I highly recommend this section of the GrapheneOS FAQ and this video.