Is it better to pay for a Hajj on behalf of a deceased father who had performed Hajj multiple times, or to pay for a Hajj on behalf of a needy person who has not yet performed it?

The scholars have not stipulated a preference between the two matters.

However, it is more appropriate to pay the amount for Hajj on behalf of the father, even if he has performed Hajj for himself, because the father has a greater right than others.

This is indicated by the words of the Almighty: "They ask you, [O Muhammad], what they should spend. Say, 'Whatever good you spend is for parents and relatives and orphans and the needy and the traveler. And whatever good you do - indeed, Allah is Knowing of it.'" (Al-Baqarah: 215).

It is possible to combine the two matters by paying the amount to someone who has not previously performed Hajj, with the intention of dedicating the reward thereof to the father.

For any act of worship one performs and dedicates its reward to a deceased Muslim, that will benefit them.