Longstreet has a reputation for 'defensive fighting'... basically, maneuvering the much larger Union forces into attacking him on ground of his own choosing. Not sure how true that is, but if it is, then Union casualties are likely to be a lot higher... but that isn't really a strategy for winning the war/taking the war to the enemy either... a longer, slower, more painful death for the CSA?
He didn't demonstrate that during the Knoxville campaign, where he was stunningly ineffective in an independent command. It says a lot when you get outsmarted by Burnside.