Show era, he’s shown to be a competent captain able to make decent strategic decisions. For instance, in the episode with the cloaking Romulan Bird of Prey, Kirk creates a battle plan which is able to take advantage of deficiencies in his foe’s ship. He’s also seen caring about making sure the crew goes into battle prepared, constantly drilling the crew so they are more responsive when time matters. Kirk is also shown as able to make hard personnel decisions which end up being right in the end. Kirk takes risks and is somewhat aggressive in playing a weak hand, but that is why he was put in command. SNW even has an episode showing that Kirk’s command is better suited to certain situations over Pike.

Movie era, Kirk isn’t as good of a captain. His crew bungle safety so bad it kills his science officer. Kirk’s rash decisions get people killed when dealing with Khan. His crew shows wild incompetence which kills a Klingon Chancellor.

It is interesting how different the character is between the shows and the movies.