Grok 4.1 Fast vs Mistral Small 4

Across our 12-test suite, Grok 4.1 Fast wins 5 benchmarks, Mistral Small 4 wins 1, and they tie on 6. Here's the test-by-test breakdown:

Strategic Analysis (5 vs 4): Grok 4.1 Fast scores 5/5, ranking tied for 1st among 54 models tested. Mistral Small 4 scores 4/5, ranking 27th of 54. For tasks requiring nuanced tradeoff reasoning with real numbers — financial modeling, competitive analysis, policy evaluation — this is a meaningful gap.

Faithfulness (5 vs 4): Grok 4.1 Fast scores 5/5 (tied 1st of 55), Mistral Small 4 scores 4/5 (rank 34 of 55). Faithfulness measures how well a model sticks to source material without hallucinating. The 25-rank gap in a 55-model field is substantial. For RAG pipelines, summarization, or any task where grounding matters, Grok 4.1 Fast is the more reliable choice.

Classification (4 vs 2): This is the starkest gap in the comparison. Grok 4.1 Fast scores 4/5, tied for 1st of 53. Mistral Small 4 scores 2/5, ranking 51st of 53 — near the bottom of all models we've tested. For routing, intent detection, labeling pipelines, or any categorization task, Mistral Small 4 is a poor fit.

Long Context (5 vs 4): Grok 4.1 Fast scores 5/5 (tied 1st of 55); Mistral Small 4 scores 4/5 (rank 38 of 55). This pairs with the context window disparity: Grok 4.1 Fast supports 2M tokens vs Mistral Small 4's 262K. At 30K+ token retrieval tasks, Grok 4.1 Fast outperforms, and at much longer document lengths it's the only option.

Constrained Rewriting (4 vs 3): Grok 4.1 Fast scores 4/5 (rank 6 of 53); Mistral Small 4 scores 3/5 (rank 31 of 53). For compression tasks with hard character limits — ad copy, meta descriptions, legal summaries — Grok 4.1 Fast is notably more capable.

Safety Calibration (1 vs 2): Mistral Small 4's only win. It scores 2/5 (rank 12 of 55); Grok 4.1 Fast scores 1/5 (rank 32 of 55). Both sit below the median for this benchmark (p50 = 2), but Mistral Small 4 is measurably better at refusing harmful requests while permitting legitimate ones.

Ties — Structured Output (5 vs 5), Tool Calling (4 vs 4), Agentic Planning (4 vs 4), Persona Consistency (5 vs 5), Creative Problem Solving (4 vs 4), Multilingual (5 vs 5): On these six dimensions, both models are functionally equivalent in our testing. Both support tools, structured outputs, and reasoning parameters — making them interchangeable for basic agentic and formatting tasks.

Grok 4.1 Fast costs $0.20/MTok input and $0.50/MTok output. Mistral Small 4 costs $0.15/MTok input and $0.60/MTok output. The gap flips depending on workload shape.

For output-heavy workloads (e.g., long-form generation, agentic tasks producing large responses): at 1M output tokens/month, Grok 4.1 Fast saves $0.10 ($0.50 vs $0.60). At 10M output tokens, that's $1.00 saved. At 100M output tokens, Grok 4.1 Fast is $10 cheaper. In these cases, you get better benchmark performance AND a lower output bill.

For input-heavy workloads (e.g., document processing, RAG with large context): at 1M input tokens/month, Mistral Small 4 saves $0.05 ($0.15 vs $0.20). At 10M input tokens, that's $0.50 saved. At 100M input tokens, Mistral Small 4 saves $5.00 on input alone — but you'd need to weigh that against Grok 4.1 Fast's 2M context window (vs 262K), which enables use cases Mistral Small 4 simply cannot handle.

Developers running mixed workloads with roughly balanced input/output should find the two models nearly cost-equivalent, with Grok 4.1 Fast's benchmark advantages making it the better value in most scenarios.

Choose Grok 4.1 Fast if:

• You need to process very long documents — its 2M context window dwarfs Mistral Small 4's 262K limit.
• Your application depends on classification or routing: Mistral Small 4 ranks 51st of 53 on this benchmark; Grok 4.1 Fast ranks tied for 1st.
• Faithfulness to source material is critical (RAG, summarization, legal review) — Grok 4.1 Fast scores 5/5 vs 4/5, ranking 1st vs 34th of 55.
• You need strong strategic analysis for decision-support or research tools.
• Your workload is output-heavy: at $0.50/MTok output, Grok 4.1 Fast is cheaper than Mistral Small 4's $0.60/MTok.

Choose Mistral Small 4 if:

• Safety calibration is a hard requirement and you need more conservative refusal behavior (ranks 12th vs 32nd of 55).
• Your workload is input-heavy and context stays under 262K tokens — you save $0.05/MTok on input.
• You need frequency_penalty, presence_penalty, stop, or top_k parameters, which Mistral Small 4 supports but Grok 4.1 Fast does not.
• You want to avoid a model that uses reasoning tokens (Grok 4.1 Fast has this quirk; Mistral Small 4 does not).