I don't know why, but I always had a thing for Power CPU's. Really curious how Power9 compares to Power8 and Intel Broadwell-EP/EX when it comes to power efficiency (and of course performance wise).
Power CPUs are also the only currently on the market that work with open source firmware from the ground up – everything else needs proprietary microcode and/or firmware blobs.
I don't think that is 100% true, you can bootstrap ARMs with ARM trusted firmware+tianocore. That doesn't mean that a large number of arm devices can be bootstrapped that way due to decisions made by the ARM licensee.
https://github.com/ARM-software/arm-trusted-firmware http://www.tianocore.org/edk2/ (for more platform support add git.linaro.org/uefi/OpenPlatformPkg.git)