Real-world advantage of namespace aliases vs defines [closed]

Answer 1

In this particular case, it depends. If using a namespace alias does the trick, by all means prefer it to macros, for all of the usual reasons. But the two do radically different things. You cannot open a namespace using its alias, i.e.:

namespace XYZ_ver1 {}
namespace XYZ = XYZ_ver1;

namespace XYZ {     //  Illegal!
}

This works with a macro; in fact, you can define the macro before the namespace has ever appeared. If you need this, then you need to use a macro.