Claude Sonnet 4.5 vs Gemini 3 Flash: Balanced AI Models for Speed and Quality Claude Sonnet 4.5 and Gemini 3 Flash are often described as “default” models, but they arrive at that position through very different design choices. Both aim to balance speed and quality. They simply define that balance in different ways. This comparison focuses on how each model behaves in everyday professional work , where neither extreme speed nor maximum reasoning depth is the sole priority. ··