وَبِهَذَا الِاعْتِبَارِ كَانَ الْأَفْضَلُ هُوَ الْقُرْآنُ
In this respect, the Qur'an is the most excellent.
The phrase “in this respect” refers back to the recited and heard arrangement. The Qur'an's excellence concerns its revealed form, guidance, recitation and distinctive merits. It does not suggest that one portion of an indivisible eternal attribute has become intrinsically more perfect than another.
Two questions must remain distinct: Is divine speech one as an attribute? May one expression of revelation have greater merit than another? The former concerns unity; the latter comparative excellence.