Because nodenv was forked from rbenv, many of the reasons to choose nodenv over others are similar to why one would choose rbenv over rvm. (Nodenv also inherits a much longer battle-tested history than others.)
One of the biggest reasons to choose nodenv over the others is that nodenv can automatically select the appropriate node version for a given project. Neither nvm nor n have auto-switching capabilities out of the box. They both require some form of 'use' command to activate a given version; which lasts for the lifetime of the shell (or until another version is activated).