Choosing a Toolchain
For a hobby project the toolchain question is nearly free: install Arm GNU, move on. For a product it is one of the longest-lived decisions in the codebase. A toolchain choice outlives the engineers who made it, because the compiler is baked into every build artefact you have ever released and into every certification argument you have ever made. Changing it later is not a flag change; it is a re-qualification.