DeepSeek V3.1 Terminus vs GPT-5.4 Nano

In our 12-test suite DeepSeek V3.1 Terminus and GPT-5.4 Nano tie on 7 tasks and Nano wins 5 tasks (DeepSeek has no outright wins). Test-by-test (score A = DeepSeek, B = GPT-5.4 Nano):

• Long context: tie (A 5 vs B 5). Both are tied for 1st for long-context retrieval in our rankings (“tied for 1st with 36 other models out of 55 tested”), so expect reliable behavior on 30K+ token inputs.
• Persona consistency: Nano wins (A 4 vs B 5). DeepSeek ranks 38/53 while Nano is tied for 1st — Nano resists persona injection and keeps character more consistently in our tests.
• Tool calling: Nano wins (A 3 vs B 4). DeepSeek ranks 47/54; Nano ranks 18/54 — for function selection, sequencing and argument accuracy, Nano showed clearer correctness.
• Classification: tie (A 3 vs B 3). Both rank 31/53, adequate for routing and basic categorization but not a differentiator.
• Creative problem solving: tie (A 4 vs B 4). Both rank 9/54; expect comparable idea generation and feasible suggestions.
• Constrained rewriting: Nano wins (A 3 vs B 4). DeepSeek ranks 31/53 vs Nano rank 6/53 — Nano is substantially better at strict compression/format constraints.
• Faithfulness: Nano wins (A 3 vs B 4). DeepSeek’s faithfulness ranks 52/55 (near the bottom) while Nano ranks 34/55 — DeepSeek shows higher hallucination risk in our tests.
• Safety calibration: Nano wins (A 1 vs B 3). DeepSeek scored 1 (rank 32/55) vs Nano 3 (rank 10/55) — DeepSeek is weak at refusing harmful requests in our testing.
• Structured output: tie (A 5 vs B 5). Both tied for 1st (“tied for 1st with 24 other models out of 54 tested”) — excellent JSON/schema reliability from either model.
• Agentic planning: tie (A 4 vs B 4). Both rank 16/54 — comparable goal decomposition and failure recovery.
• Strategic analysis: tie (A 5 vs B 5). Both tied for 1st — strong numeric tradeoff reasoning from either model.
• Multilingual: tie (A 5 vs B 5). Both tied for 1st in multilingual quality. Additionally, GPT-5.4 Nano scores 87.8% on AIME 2025 (Epoch AI), ranking 8th of 23 on that external math benchmark — useful evidence of its high-end math reasoning. Overall, Nano’s wins concentrate on safety, faithfulness, persona, tool-calling and constrained rewriting — properties important for live, user-facing and agentic applications; DeepSeek’s value is cost and parity on long context, structured output, strategic analysis and multilingual output.

Per‑mTok pricing: DeepSeek V3.1 Terminus charges $0.21 input / $0.79 output; GPT-5.4 Nano charges $0.20 input / $1.25 output. If your workload has a 50/50 input/output token split, 1M total tokens ≈ 1,000 mTok (500 mTok input + 500 mTok output): DeepSeek ≈ $500 (500×$0.21 + 500×$0.79), GPT-5.4 Nano ≈ $725 (500×$0.20 + 500×$1.25). At 10M tokens/month the monthly bill is ≈ $5,000 (DeepSeek) vs $7,250 (Nano); at 100M tokens it's ≈ $50,000 vs $72,500 — a savings of $2,250 per 10M or $22,500 per 100M tokens. The payload’s priceRatio (0.632) reflects that DeepSeek costs ~63.2% of Nano for comparable mixes. High-volume, price-sensitive teams (batch generation, background processing) should care most; teams that need tighter safety, fewer hallucinations, or better tool integration should accept Nano’s higher output cost.

Choose DeepSeek V3.1 Terminus if you need: large-context or structured-output workflows at scale where cost is the priority (it ties Nano on long-context, structured output, strategic analysis and multilingual benchmarks and costs ~37% less in comparable mixes). Example use cases: batch document summarization, large-context retrieval pipelines, multilingual bulk generation, or non-customer-facing back-end jobs. Choose GPT-5.4 Nano if you need: safer, more faithful, persona-consistent, tool-enabled interactions or strict constrained rewriting (Nano wins safety calibration, faithfulness, persona consistency, tool calling and constrained rewriting). Example use cases: customer-facing chatbots, agentic tool orchestration, production moderation, or apps that cannot tolerate hallucinations. If you run high-volume, non-critical tasks and want the lowest bill, pick DeepSeek; if production safety and correctness matter more than per-token cost, pick GPT-5.4 Nano.