Some significant differences exist between the Qur’an and New Testament in terms of their preservation and transmission.
1- The Qur’an was written during the lifetime of the Prophet (peace be upon him) and canonized by his companions who knew him personally. The New Testament, on the other hand, was written after the alleged death of Jesus and canonized by people who never knew him.
2- The mode of revelation is different. The Qur’an was not revealed as a written text, while the New Testament was.
3- The mode of transmission is different for the two books. The New Testament is transmitted via manuscripts only. When an error occurs in one manuscript, be it deliberate or unintentional, it is often copied by the next scribe making a copy of this manuscript. However, the Quran is transmitted both orally and in writing. The two keep a check on each other, thus eliminating errors.
4- The Qur’an is preserved in its original language, while the Gospels cite people speaking in a different language. Thus, much could be lost through translation, while this does not apply to the Qur’an.
5 - The New Testament is a collection of books authored by multiple authors in different locations over a roughly estimated range of twenty to eighty years, whereas the Quran is one book with one author in no more than two locations within no more than twenty-three years.
6 - The Qur’an was revealed in seven modes, which are all considered divine revelation. This means that Islam teaches that there are divinely inspired variants while no such escape route exists for the Bible.
For point 1, I would replace "death of Jesus" with "alleged death of Jesus".