I've design with Intel Atoms and ARM chips. Atoms are very bloated and require a lot of external support to get up and running. Intel's firmware/boot support is

I've design with Intel Atoms and ARM chips. Atoms are very bloated and require a lot of external support to get up and running. Intel's firmware/boot support is atrocious. They still have PC OEM's in mind. ARM chips on the other hand are much easier/cheaper to design for. The SoC is better integrated and targeted towards a low overall BOM cost. Core M is worse than Atom.