The virtue of an accepted Hajj that is mentioned in a hadith is general and is applicable to both obligatory and voluntary Hajj

Praise be to Allah.

There are a number of hadiths that speak of the virtue of Hajj, including the following: 

1.     The hadith narrated by al-Bukhaari (1521) and Muslim (1350) from Abu Hurayrah (may Allah be pleased with him) who said: I heard the Prophet (blessings and peace of Allah be upon him) say: “Whoever performs Hajj and does not commit any obscenity or commit any evil will go back (free of) sin as on the day his mother bore him” 

2.     Al-Bukhaari (1773) and Muslim (1349) narrated from Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “…an accepted Hajj brings no reward but Paradise.” 

3.     At-Tirmidhi (738) and an-Nasaa’i (2631) narrated that ‘Abdullah ibn Mas‘ood said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Make the Hajj and ‘Umrah follow each other closely, for they remove poverty and sins as the bellows removes the dross of iron, gold and silver, and an accepted Hajj brings no less a reward than Paradise.” Classed as hasan by Shaykh al-Albaani in Saheeh Sunan at-Tirmidhi 

The virtue mentioned in the hadiths quoted above includes both the obligatory Hajj and the naafil (supererogatory) Hajj, because of the general meaning of the wording. 

As the scholars (may Allah have mercy on them) said, the accepted Hajj is that which is not mixed with sin. 

Shaykh Ibn Baaz (may Allah have mercy on him) said: The accepted Hajj is that in which a person does not commit any acts of disobedience towards Allah, as is indicated by the words of the Prophet (blessings and peace of Allah be upon him) in the report narrated from him by Abu Hurayrah: “Whoever performs Hajj and does not commit any obscenity or commit any evil will go back (free of) sin as on the day his mother bore him”

End quote from Majmoo‘ Fatawa Ibn Baaz (16/334) 

And Allah knows best.