For many workflows involving real time human interaction, such as voice assistant, this is the most important metric. Very few tasks are as sensitive to quality, once a certain response quality threshold has been achieved, as is the software planning and writing tasks that most HN readers are likely familiar.
The way that voice assistants work even in the age of LLMs is
Voice —> Speech to Text -> LLM to determine intent -> JSON -> API call -> response -> LLM -> text to speech.
TTFT is irrelevant, you have to process everything through the pipeline before you can generate a response. A fast model is more important than a good model
Source: I do this kind of stuff for call centers. Yes I know modern LLMs don’t go through the voice -> text -> LLM -> text -> voice anymore. But that only works when you don’t have to call external sources