There is no winner — there is a right answer for your target, your fleet size and who maintains it.
Three questions decide this, and they decide it quickly. What are you updating — a Linux system or a microcontroller? Who runs the server — you or a vendor? And how much does a bricked device cost you? Answer those honestly and the shortlist is usually two names long.
The default for embedded Linux. A/B rollback is the safest model in wide deployment, and the open-source edition is real enough to ship on.
The default for microcontrollers, especially Zephyr. Consumption pricing means you can calculate the bill instead of negotiating it.
When you need to know why a device failed, not just that it stopped reporting. Expensive, and worth it on fleets where field failures are costly.
If your team already ships containers, this converts firmware updates into a workflow they know.
When per-device fees are unacceptable at your scale and you have someone to operate a server.
Choose the rollback story first and the feature list second. Every platform here can deliver bytes to a device; they differ in what happens when those bytes are wrong.
Tell us the target hardware, roughly how many devices, and what happens commercially if one bricks. You get back a shortlist and the reasoning. No vendor is given your details.