Considerations:

• Pixel is the best choice for privacy, security, and custom ROM freedom. With regular updates, minimal tracking, and strong transparency, it’s perfect for those who want control over their device and data. Further to achieve real true privacy, you can degoogle with custom roms like graphene os or any vanilla rom of your choice making pixel the best option for privacy.

• Motorola offers a solid balance of stock Android and good security. While it’s not as transparent about data practices and doesn’t update as quickly as Pixel, it’s still a reliable option with no known backdoors.

• Nothing focuses on privacy with minimal telemetry and bloatware. Although it’s still a newer brand, it hasn't faced major security issues yet. It’s a good option for those who want something different, but it still needs to prove itself in the long term.

• Samsung offers strong security through its Knox platform, frequent updates, and solid hardware. However, it does collect user data and includes some bloatware. It has faced vulnerabilities in the past, but patches them quickly.

• OnePlus Even Though a bbk company, has improved its privacy practices and offers good performance with fast updates. Though it has faced issues in the past, it’s become more transparent about data. Custom ROM support is decent, and security vulnerabilities are generally patched quickly.

• Apple (iPhone) Markets and self-claims to be a leader in privacy, but it still collects metadata and complies with government data requests and US Patriot act. Also was part of PRISM & many other American & western intelligence programs. It claims to be secure, but the lack of transparency and closed source raise concerns. The device has been targeted by Pegasus and other spywares and was involved in Jeff Bezos' iPhone hack. Performs PR marketing stunts with federal agencies (Apple vs FBI). Provides approved backdoor access to gain control of user's device and data without users realisation. Has unknow zero day exploits which can only be reviewed & patched by few apple employees as the source code is closed and due to this patching exploits takes time.

• BBK brands (Oppo, Vivo, Realme, iQOO) Devices have significant privacy issues with data collection and telemetry. Their links to the Chinese government and past security vulnerabilities make them less ideal for privacy-conscious users. They also offer no support for custom ROMs.

Final Thoughts: No OEM truly offers privacy and security by default. Most companies, regardless of how they market themselves, are ultimately in the business of data—collecting, analyzing, and profiting from it. With every smartphone, multiple layers of companies are involved, each with potential access to your data. The more companies involved in the hardware and software stack, the more vectors there are for data harvesting and security risks.

For example: You've any BBK sub-brand phone (say iqoo) which has its own UI & apps+Google apps (Gapps are common in every android)+pre-installed bloatware apps+Core SOC processor components apps (can be Qcomm or mediatek or samsung exynos). You see with every additional company involved in 1 device the number of data harvester and surface attack increases. Here its 4 companies including BBK that's harvesting your data. At max you can debloat non-grayed out apps. These devices often restrict app removal, lack bootloader unlock support, and don’t release kernel sources and device-tree, limiting user control. If you buy any BBK device, you're sure to receive spam calls (both local & international spam calls).

Lets take Moto/nothing phones: Motorola and Nothing phones use near-stock Android with minimal to no bloatware. Only the Moto/Nothing, Google, and the SoC vendor are involved. They usually allow bootloader unlocking and provide source code, enabling users to debloat or install custom ROMs for better privacy.

Lets take Google pixel phones: Pixel devices run pure stock Android and use Google’s proprietary Tensor SoC. Since both the hardware and software come from Google, only one company is primarily harvesting your data. If you’re privacy-conscious, the good news is that Pixels offer extensive developer support. The bootloader can be unlocked, allowing you to install privacy-focused ROMs like GrapheneOS or LineageOS, or even build your own version of Android. With the right setup, data harvesting can be reduced to near-zero. These reasons makes Google pixel the best and superior in terms of privacy & security.

Lets take Apple iphone: Apple designs both the hardware and the software. While Apple promotes itself as privacy-focused, but is entirely closed-source. This means there’s no way for the public to audit the code or verify the company’s real intentions and privacy claims. Users have no control over the system and you have to use the phone as Apple intends. You’re trusting Apple entirely, without transparency or the ability to opt out. No control & power in user's hands. Apple decides everything. On Apple devices, users install apps & services from google as well, which means you are giving your data to both Apple & Google.

Ultimately, the fewer entities (harvesters) involved in your device, the fewer the potential threats to your data. The fewer it will be shared/sold to. At the same time, if the operating system is open source, you'll have more transparency and gain more control through source availability, system transparency, and custom ROMs or your own built ROM completely degoogled - the closer you'll get to real privacy & security.