The truly amusing fact of the matter is that, whilst he has a far grimmer and more blunt manner, Theodred is actually the far better politician in a competition between him and Boromir. He may have less patience overall, but he has a great deal more patience for the individual concerns of the Thanes and Reeves of the riddermark, along with a running catalogue of those various concerns that he keeps in his thoughts at all times. In this actually Theodred is more like Boromir’s father than Boromir is himself.
And indeed, far more of Theodred’s actions as Prince and Marshall were politically based, be it solving squabbles, arranging marriage matches, manoeuvring allies into positions of social strength and brokering peace between feuding families, this was the meat of Theodred’s accomplishments in service of Rohan. It was forever a bitten frustration of his that, as his Father’s illness and Grima’s influence progressed, this work became more and more impossible for him to do.