Both build a custom Linux image for your board. The difference shows up eighteen months later, when you need to add a package, patch a CVE, or hand the project to a new engineer.
Once a product's application processor is running Linux — a Cortex-A class part like an NXP i.MX, a TI Sitara, or a Raspberry Pi Compute Module doing heavier edge compute than a microcontroller can handle — the next decision is what builds the OS image. The two dominant open-source options, Yocto and Buildroot, solve the same problem with very different philosophies.
Buildroot uses a single Kconfig-style menu and Makefiles to cross-compile a minimal root filesystem plus kernel and bootloader. Builds are fast, the mental model is small, and for a product with a fixed, modest package list — a headless gateway, a single-purpose sensor hub — it's often the faster path to a working image. The tradeoff is that Buildroot doesn't really do "layers" or long-term package management the way Yocto does; every customization tends to live as a patch or a defconfig, which works fine until the product's software surface grows.
Yocto (via the BitBake build engine and OpenEmbedded layers) is heavier to learn and slower on a first build, but it's designed for exactly the situation Buildroot struggles with: a product line with multiple hardware variants, a multi-year maintenance window, and package/dependency management that needs to survive turnover on the engineering team. Vendor BSPs (board support packages) for most Cortex-A application processors are typically published as Yocto meta-layers first, which matters if you're building on a semi-custom carrier board around a vendor SoM.
The real question isn't "which is better" — it's how long the image needs to be maintained and how many hardware variants it needs to support. We default to Yocto, especially for complex, scalable product lines — gateways running on parts like NXP's i.MX8, for example. Yocto's layer management earns its overhead when we're building a multi-variant hardware line that needs long-term maintainability and OTA update infrastructure. We only drop down to Buildroot for highly constrained, single-purpose devices, where a rapid, lightweight root filesystem is the goal and maintaining custom meta-layers would be overhead the product doesn't need. This decision sits alongside the RTOS-vs-bare-metal call covered in RTOS vs. bare-metal, and connects to our firmware work more broadly.
