Which is better and more rewarding: fasting the first days of Dhul-Hijjah or fasting the ninth day of Dhul-Hijjah?

Fasting on the Day of Arafat expiates the sins of two years, but it is disliked for the pilgrim at Arafat so that it does not weaken him from supplicating and performing the rituals of Hajj. As for fasting the first days of Dhul-Hijjah, it is legislated and recommended, as it was narrated that the Prophet, peace and blessings be upon him, used to fast them, and righteous deeds during them are beloved to Allah.