أَوْ ذِكْرُ اللَّهِ تَعَالَى فِيهِ أَكْثَرُ
Or because mention of Allah Most High is more abundant in it.
A surah that prominently expounds God's oneness, names, attributes or majesty may have a special merit in recitation. The relevant comparison concerns the subject discussed and the effect of its recitation.
It does not imply that verses about laws, history or moral instruction are less divine. Different Qur'anic subjects carry guidance and wisdom; a particular merit in one surah is not a devaluation of another.