Which is worse in the sight of Allah: shirk (polytheism) or kufr (disbelief), and which deserves more punishment on the Day of Resurrection? And are the People of the Book considered polytheists, disbelievers, or believers?

We have previously clarified the difference between shirk (polytheism/associating partners with God) and kufr (disbelief), and that every mushrik (polytheist) is a kafir (disbeliever), and every kafir is a mushrik, and both are eternally in the fire of Hell. As for which is greater, shirk or kufr? The forms of shirk are many, as are those of kufr. Some types of kufr are greater than shirk, such as denying the existence of the Creator, عز وجل (Exalted and Glorified be He); this is greater than the shirk of one who worships another alongside Allah. Al-Hafiz Ibn Hajar said: "Some kufr is more heinous than shirk." As for the People of the Book, they are the Jews and Christians, and they are disbelievers (kuffar) and polytheists (mushrikun), not believers. Allah has judged them to be disbelievers in the Quran, as in His saying, the Almighty: ﴿إِنَّ الَّذِينَ كَفَرُوا مِنْ أَهْلِ الْكِتَابِ وَالْمُشْرِكِينَ فِي نَارِ جَهَنَّمَ خَالِدِينَ فِيهَا﴾ [Al-Bayyinah: 6] (Indeed, those who disbelieved among the People of the Book and the polytheists will be in the fire of Hell, abiding eternally therein), and His saying, the Almighty: ﴿لَقَدْ كَفَرَ الَّذِينَ قَالُوا إِنَّ اللَّهَ ثَالِثُ ثَلَاثَةٍ﴾ [Al-Ma'idah: 74] (Certainly, disbelieved are those who say that Allah is the third of three).