GPT-5 Nano vs Grok 4.20

Head-to-head outcomes (our 12-test suite): Grok 4.20 wins on strategic analysis (5 vs 4), constrained rewriting (4 vs 3), creative problem solving (4 vs 3), tool calling (5 vs 4), faithfulness (5 vs 4), classification (4 vs 3), and persona consistency (5 vs 4). GPT-5 Nano wins safety calibration (4 vs 1). They tie on structured output (both 5), long context (both 5), agentic planning (both 4), and multilingual (both 5). Context and rankings: Grok’s 5 on tool calling is tied for 1st of 54 models (tied with 16 others), while GPT-5 Nano’s 4 on tool calling ranks 18 of 54 — meaning Grok is in the top tier for reliable function selection and sequencing in our tests. On faithfulness Grok’s 5 is tied for 1st of 55 (with 32 others) versus GPT-5 Nano’s 4 (rank 34 of 55), indicating Grok makes fewer source-hallucination errors in tasks we measured. For strategic analysis Grok ranks tied for 1st (1 of 54) vs GPT-5 Nano’s rank 27 — Grok produced stronger nuanced tradeoff reasoning in our scenarios. GPT-5 Nano’s advantage in safety calibration (score 4, rank 6 of 55) means it refused harmful requests and allowed legitimate ones more accurately in our tests; Grok scored 1 (rank 32), so Grok was stricter or less calibrated on that axis in our runs. Additional external math data: GPT-5 Nano scores 95.2% on MATH Level 5 and 81.1% on AIME 2025 (Epoch AI), which supports its strength on math-heavy tasks in external benchmarks. Practically: pick Grok for automation, tool-enabled agents, and high-fidelity extraction/classification; pick GPT-5 Nano when safety calibration, math accuracy, long contexts, or cost are decisive.

Costs shown are per thousand tokens (mTok). Assuming a 50/50 split of input/output tokens: GPT-5 Nano (input $0.05, output $0.40) costs $225/month for 1M tokens (500 mTok input = $25; 500 mTok output = $200). Grok 4.20 (input $2, output $6) costs $4,000/month for 1M tokens (500 mTok input = $1,000; 500 mTok output = $3,000). Scale multiples: at 10M tokens/month GPT-5 Nano ≈ $2,250 vs Grok ≈ $40,000; at 100M GPT-5 Nano ≈ $22,500 vs Grok ≈ $400,000. The gap matters most for high-volume apps (SaaS, analytics, large-scale chat) and cost-sensitive startups — GPT-5 Nano reduces run costs by an order of magnitude under these assumptions. Teams focused on low-volume, high-reliability automation or where tool-calling/faithfulness reduces downstream human effort may justify Grok’s higher spend.

Choose GPT-5 Nano if you need dramatically lower per-token costs, strong long-context handling, safer refusal behavior, or high math performance (95.2% MATH Level 5 and 81.1% AIME 2025 per Epoch AI). Choose Grok 4.20 if your priority is best-in-class tool calling, faithfulness, strategic analysis, classification, or persona consistency and you can absorb higher running costs ($2/$6 per mTok).