The difference mainly lies in status of this verse, whether it is a permanent part of Quran (i.e. part of each Surah separately) or it has an independent existence irrespective of Surahs, but its transmission with Quran has never been questioned. Some of the scholars regard the difference of opinion similar to the kind of difference of opinion among the leading scholars of recitation about some words and letters that may be proven in some recitations and not in others.
According to Ghamidi Sahab, it is part of Quran (at the start of each Surah) but has an independent existence.
Qazi Ayaz wrote:
…”The Muslims are unanimously agreed that the Quran which is recited in all parts of the world and is written in the Mushaf that the Muslims have, that is contained between the two covers, from the first Surah “All the praises and thanks be to Allah, the Lord of the Alameen (mankind, jinns and all that exists)” to the last Surah, “Say: “I seek refuge with (Allah) the Lord of mankind”, is the Book of Allah and His Revelation that He sent down to His Prophet Muhammad (blessings and peace of Allah be upon him), and that everything in it is true, and that anyone who deliberately takes away a single letter from it or changes one letter for another or adds a letter to it, that is not included in the Mushaf on which there is consensus, and there is consensus that it is not part of the Quran – the one who does any of these things deliberately is a disbeliever“.
(Ash-Shifa bi Tareef Huqooq al-Mustafa, 2/304, 305)
Please also read the following Article “Quran Transmission through The Ages“: