Gemini 3.1 Pro Preview vs GPT-4o-mini

Gemini 3.1 Pro Preview wins 9 of 12 internal benchmarks, ties 1, and loses 2. Here is the breakdown:

Where Gemini 3.1 Pro Preview leads:

• Creative problem solving: 5/5 vs 2/5. Gemini 3.1 Pro Preview is tied for 1st among 54 models; GPT-4o-mini ranks 47th of 54. This is a substantial gap for tasks requiring novel, feasible ideas.
• Strategic analysis: 5/5 vs 2/5. Gemini 3.1 Pro Preview is tied for 1st among 54 models; GPT-4o-mini ranks 44th of 54. Nuanced tradeoff reasoning with real numbers is a clear Gemini strength.
• Faithfulness: 5/5 vs 3/5. Gemini 3.1 Pro Preview is tied for 1st among 55 models; GPT-4o-mini ranks 52nd of 55 — near the bottom. For summarization, RAG pipelines, and any task where hallucination is costly, this gap is operationally significant.
• Agentic planning: 5/5 vs 3/5. Gemini 3.1 Pro Preview is tied for 1st among 54 models; GPT-4o-mini ranks 42nd of 54. Goal decomposition and failure recovery are core to autonomous workflows.
• Long context: 5/5 vs 4/5. Gemini 3.1 Pro Preview is tied for 1st among 55 models; GPT-4o-mini ranks 38th of 55. Combined with a 1,048,576-token context window versus GPT-4o-mini's 128,000, this makes Gemini 3.1 Pro Preview the clear choice for large document analysis.
• Structured output: 5/5 vs 4/5. Both are solid, but Gemini 3.1 Pro Preview is tied for 1st; GPT-4o-mini ranks 26th of 54.
• Persona consistency: 5/5 vs 4/5. Gemini 3.1 Pro Preview tied for 1st; GPT-4o-mini ranks 38th of 53.
• Multilingual: 5/5 vs 4/5. Gemini 3.1 Pro Preview tied for 1st among 55 models; GPT-4o-mini ranks 36th of 55.
• Constrained rewriting: 4/5 vs 3/5. Gemini 3.1 Pro Preview ranks 6th of 53; GPT-4o-mini ranks 31st of 53.

Where GPT-4o-mini leads:

• Safety calibration: 4/5 vs 2/5. GPT-4o-mini ranks 6th of 55; Gemini 3.1 Pro Preview ranks 12th of 55 (tied with 19 others). This measures accurate refusal of harmful requests while permitting legitimate ones — GPT-4o-mini is meaningfully better calibrated in our testing.
• Classification: 4/5 vs 2/5. GPT-4o-mini is tied for 1st among 53 models; Gemini 3.1 Pro Preview ranks 51st of 53. For routing, categorization, and labeling pipelines, GPT-4o-mini is a much better fit.

Tied:

• Tool calling: Both score 4/5, both rank 18th of 54 in our tests.

External benchmarks (Epoch AI): On AIME 2025 (math olympiad), Gemini 3.1 Pro Preview scores 95.6% — ranking 2nd of 23 models with that external score in our dataset, above the 90th percentile benchmark of 90%. GPT-4o-mini scores just 6.9% on AIME 2025, ranking 21st of 23, and 52.6% on MATH Level 5, ranking 13th of 14. These external results reinforce the internal benchmark signal: Gemini 3.1 Pro Preview is a significantly stronger reasoning model, while GPT-4o-mini is not competitive on advanced math tasks.

GPT-4o-mini costs $0.15 per million input tokens and $0.60 per million output tokens. Gemini 3.1 Pro Preview costs $2.00 per million input tokens and $12.00 per million output tokens — a 13x gap on input and a 20x gap on output. At 1 million output tokens per month, GPT-4o-mini runs you $0.60 versus $12.00 for Gemini 3.1 Pro Preview — an $11.40 difference that's easy to absorb. At 10 million output tokens, that gap grows to $114. At 100 million output tokens, you're spending $1,200 with GPT-4o-mini versus $12,000 with Gemini 3.1 Pro Preview — a $10,800 monthly delta. Developers running high-throughput pipelines (bulk classification, triage, simple Q&A) should take the cost gap seriously. Gemini 3.1 Pro Preview's pricing is justified for workflows that genuinely require its capabilities: long-context retrieval across 1M-token windows (versus GPT-4o-mini's 128K), agentic task planning, or complex reasoning — where the output quality difference translates to measurable downstream value.

Choose Gemini 3.1 Pro Preview if:

• Your workflow involves agentic planning, multi-step reasoning, or autonomous task execution — it scores 5/5 vs 3/5 on agentic planning in our tests.
• You need to process long documents or codebases — its 1,048,576-token context window dwarfs GPT-4o-mini's 128K, and it scores 5/5 vs 4/5 on long-context retrieval.
• Faithfulness to source material is critical (RAG pipelines, legal summarization, citation tasks) — it scores 5/5 vs 3/5, ranking 1st vs 52nd of 55 models.
• You need strong multilingual output, strategic analysis, or creative problem solving.
• You are working with audio or video inputs — Gemini 3.1 Pro Preview supports text+image+file+audio+video modalities; GPT-4o-mini handles text+image+file only.
• Advanced math or reasoning is central to your use case — 95.6% on AIME 2025 (Epoch AI) versus GPT-4o-mini's 6.9%.

Choose GPT-4o-mini if:

• You are running high-volume classification, routing, or labeling at scale — it scores 4/5 vs 2/5 and is tied for 1st of 53 models on classification, at a fraction of the cost.
• Safety calibration matters for your deployment — it scores 4/5 vs 2/5, ranking 6th of 55 models in our tests.
• Budget is the primary constraint — at $0.60/M output tokens versus $12/M, GPT-4o-mini is 20x cheaper and still capable for simpler tasks.
• Your tasks are straightforward enough that the quality gap does not justify the cost premium: simple Q&A, basic summarization, lightweight assistants.
• You need logprobs or presence/frequency penalty controls — these parameters are supported by GPT-4o-mini but not listed for Gemini 3.1 Pro Preview in our data.