1. A vehicular speech recognition system comprising: a display control unit that is mounted to a vehicle and includes a speech recognition apparatus; a navigation unit that is mounted to the vehicle, is connected to the display control unit, and includes a speech recognition apparatus; and a speech recognition controller that, when speech recognition of an inputted speech is performed individually by the speech recognition apparatus of the display control unit and the speech recognition apparatus of the navigation unit, selects and adopts one result of the speech recognition from among a result of the speech recognition of the display control unit and a result of the speech recognition of the navigation unit based on contents of the result of the speech recognition of the display control unit and contents of the result of the speech recognition of the navigation unit, wherein: the plurality of speech recognition apparatuses have different recognition dictionaries for the speech recognition, the recognition dictionaries have different command-recognition dictionaries for the speech recognition of commands, and when the result of the speech recognition by the speech recognition apparatus of the display control unit represents only a command, the speech recognition controller adopts the result of the speech recognition by the speech recognition apparatus of the display control unit.