Who won when War admiral and Sea biscuit raced?

I'm not sure what differences you are asking about. The characteristic differences of the two horses are abundant. Although Biscuit and Admiral were related (uncle/nephew) they were very different individuals.

War Admiral, son of the legendary Man-O-War, was trained by Sunny Jim Fitzsimmons who was no stranger to the winner's circle. War Admiral had won almost every prestigious race on the east coast, including the Triple Crown. He was voted Horse of the Year, and many other honors befitting a racehorse of his caliber. And as is true of many racehorses, he had a nasty temperment.

Seabiscuit, on the other hand impressed few. Fitzsimmons took a pass on the Biscuit, thinking him lazy and not worth the trouble. For those who don't know much about the racing buisiness this is a common scenario. Of the thousands of foals born every year, a Triple Crown winner is rare. Seabiscuit had some conformation faults that didn't help his case. And in a buisiness where a horse peaks at the age of three or four, Biscuit was a late bloomer, maturing later not sooner. He also had a bad temperment, mostly from mismanagement and harsh training tactics.

Going into the great match race of November 1, 1938, Seabiscuit was the longshot. Although the 2003 movie took some artistic licence with the facts, the match race was accurate. With George 'The Iceman' Wolfe up, he knew the horse and how he needed to be ridden. It truly was a David and Goliath story.

Point of interest:Seabiscuit's lifetime earnings (almost 1/2 million dollars) at the time of his retirement in 1940, far surpassed War Admiral's.