Endianness
All POWER CPU's from POWER3 onward support both big-endian (BE) and little-endian (LE) modes.[1] This is in contrast to x86, which supports only little-endian mode.
Operating System Support
Some distros only support BE; others only support LE; others support both. See the Operating System Compatibility List to check support in your preferred distro.
Security
BE mode has a security advantage over LE mode: there exist certain classes of memory-safety bugs (e.g. accessing a variable with the wrong data size) that typically cause an immediate crash (or otherwise obviously-wrong behavior) in BE mode, but instead manifest as silent security vulnerabilities in LE mode. Theoretically, it is likely that a sanitizer could achieve similar security benefits in LE mode, but such a sanitizer would have a performance impact that usage of BE mode would not incur. (Also, no such sanitizer is currently known to exist.)
