I didn’t see any info on the intent of these macros in the docs. Seems like they ultimately expand to “Serial”, but not sure what the recommended best practice is.
Just looked in the debug/watch node, and it uses XOD_DEBUG_SERIAL, but without any #ifdef. My nodes wouldn’t compile without the #ifdef. The only difference I can see is several #pragma statements at the beginning of debug/watch, but they seem unrelated.