Gemini earns its place on jobs where the input is large or is not text. Reading a whole product manual to answer a fit question, checking that product imagery matches the description, or working across a long support history without losing the thread.
We reach for it when those traits matter, and for something else when they do not. If your data already lives in BigQuery it is also the model with the shortest path to it. The choice of model is usually less important than what you connect it to, and we would rather spend the effort on the retrieval layer than on the badge.