alt Hacker NewsGreatly improved privacy and security and end-user control of your phone and its data. In those areas, possibly the best option, though iPhones might be better in security (not necessarily the other two areas) - Apple has a slightly bigger budget and a few more engineers, and directly controls the hardware.
GrapheneOS exists to greatly improve the privacy and security of an existing open source OS project. Android Open Source Project has good privacy and security as a starting point.
Pixels provide strong hardware and firmware security. Pixels have made multiple significant hardware and firmware level improvements based on recommendations by GrapheneOS. GrapheneOS now has a hardware partnership with Motorola Mobility which includes working with Qualcomm. It isn't only a software project.
Regularly leaked data on the capabilities of Cellebrite show they have the least success with GrapheneOS by far despite specifically hiring for it based on their job postings.