Decision models trail language models on knowledge and reasoning, but are faster and cheaper

Decision models offer significant speed and cost advantages over language models, but trail on knowledge and reasoning. On classification and tool-calling tasks, leading decision models perform comparably to language models while being significantly faster and cheaper. However, language models outperform on knowledge and reasoning. Claude Haiku 5.5 (Low) scores 61 on the Decision Index, 3 points ahead of Jev 1.13, but takes 1.4 seconds per task vs. 0.13 seconds (11x slower) and costs $184 per 1M Tasks vs. $42 for Jev 1.13 (4.4x more expensive)