What is best concerning the Adhha sacrifice

Question :

Which of them is best for the Adhha sacrifice, a ram or a cow?

Answer:

The best animal to slaughter for the Adhha sacrifice is the camel, then the cow, then the sheep, then to share in the slaughter of a she-camel or a cow. This is due to the Prophet's statement concerning Al-Jumu'ah:
"Whoever goes (to the Jumu'ah prayer) during the first hour, it is as if he sacrificed a camel; and whoever goes during the second hour, it is as if he sacrificed a cow; and whoever goes during the third hour, it is as if he sacrificed a horned ram; and whoever goes during the fourth hour, it is as if he sacrificed a chicken; and whoever goes during the fifth hour, it is as if he sacrificed an egg.

The point of proof from this is the presence of some preference in drawing near to Allâh, between the camels, the cows and the sheep. There is no doubt that the Adhha sacrifice is from the greatest forms of drawing near to Allâh, and the camel is the most expensive animal, with the most meat and the most benefit. This was the view held by the three Imams, Abu Hanifah, Ash-Shafi'i and Ahmad. Malik said that the one-year- old sheep was the best, then the cow, then the camel, because the Prophet sacrificed two rams and he would only do what was best. The answer to this is that it is said that he might chose that which was not the best as a way of being gentle with his Ummah, because they would follow him and he did not like to make things difficult for them. However, he explained the virtue of the camel over the cows and the sheep as was mentioned previously. And Allâh knows best.

Source:
The Permanent Committee
Fatawa Islamiyah, Vol. 4 Pages 329-330