having just finished some extensive reading on the war in the Pacific, I'd say Spruance and Mitscher were the better admirals.
Either one but at the end of the war they decided to promote only a limited number of Admirals to 5 star or Fleet admiral. Halsey was promoted owing to his public popularity.
Leahy
King
Nimitz
Halsey
Were the men.
King’s own daughter said he was an extremely even tempered man. He was just angry all the time.
Leahy was a career servant of the United States.
Nimitz was an outstanding engineer, organizer and leader.
Halsey was deserving of his moniker “Bull”. When his own son went missing over the South Pacific he was told, walked to the window, said nothing for a bit and then, still looking out the window said, “Standard search protocol.” His son was found safely. He also flew into a rage when Nimitz signaled “the world wonders” when he asked where he had gone off to with the carriers as Taffy 3 fought against overwhelming odds to protect the Leyte Gulf invasion fleet. He twice sailed into typhoons with great losses. The second time against good advice. He would have been, should have been court martialed if he were not such a hero in the public eye.
Marc Mitscher contributed one of the most important innovations of the Pacific War. He was responsible for developing the Fast Carrier Task Force which became the main offensive weapon of the US Navy.
Mitscher figured out that if you grouped four fast carriers together with their support ships that they could defend themselves with their Combat Air Patrol while sending around 500 planes out after the enemy.
At that point the Navy could move at will with little regard for what Japan chose to do.
The Task Force was numbered 58 or 38 depending upon whether Spruance or Halsey was in charge. Mitscher served with Spruance, McCain with Halsey. Everyone reported to Nimitz.
http://www.taskforce58.org/task-force-58-task-force-38/