Is the difference of opinion among the Salaf regarding the ruling on one who abandons prayer and one who rules by other than what Allah has revealed a valid difference of opinion, and who are those who differed on this matter?

The disagreement concerning the ruling on one who abandons prayer is specific to those who acknowledge its obligation. The majority of the Salaf held the view that abandoning prayer constitutes disbelief, and the preferred view is that it is major disbelief (kufr akbar). As for ruling by other than what Allah has revealed, if it is done while acknowledging that Allah's ruling is more complete, then it is minor disbelief (kufr duna kufr). However, preferring man-made laws and believing that Allah's law is not suitable for the present time constitutes major disbelief. The scholarly disagreement exists regarding whether one who rules by other than what Allah has revealed, while believing that Allah's law is more complete and righteous, is guilty of major disbelief or minor disbelief, due to the different descriptions mentioned in the Quran (the disbelievers, the defiantly disobedient, the wrongdoers).