A modal variation of the raw text input, prompt authoring using natural language can be fast & intuitive in the right circumstances.
Speaking is a natural form of expression (For those capable) which means is widely applicable for many user types, however, it still inherently requires users to understand how to author an effective prompt.
The environmental context becomes more important when considering oral input. Contextual considerations like "Is it polite for the user to speak out loud", "Can they be heard, is their context quiet?" & "Does the user want others hearing the input?"