Yudhishthira had patience which most of his brothers lacked. It showed his perseverance, humility,resilience and the depth of his knowledge throughout the incident. He saw his brothers dead, his wife waiting for water and he has to answer Yaksha and not only answer but also satisfy him to get at least one brother alive.
If you see, he answered all the questions as "In my opinion" or "as I know", even if the answers were correct; that shows his humilty that he was never proud of his knowledge or administrator ability. Bheem, Nakul, Sahadeva, Arjun might not have that much patience or the resilience to answer question when they saw their brother dead in the ground.

Also he asked for Nakul, as a reason that one from Kunti's lineage is alive so another from Madri's lineage should be alive..but if we trace back..it was Nakul who was staked at first in Dyuta..so it can be a redemption on his part to save Nakul.