GPT-5 vs Grok 4.20

Overview: in our testing GPT-5 wins two benchmarks outright (safety calibration and agentic planning), Grok 4.20 wins none, and the models tie on the majority of other tests. Detailed walk-through (scores are our 1-5 internal ratings unless otherwise noted):

• tool calling: GPT-5 5 vs Grok 4.20 5 — tie. Both score 5 and are tied for 1st of 54 models ("tied for 1st with 16 other models"), so both handle function selection, argument accuracy, and sequencing at the top of our suite.
• faithfulness: GPT-5 5 vs Grok 4.20 5 — tie and tied for 1st of 55 models; expect both to stick closely to sources in tasks where hallucination avoidance matters.
• long context: GPT-5 5 vs Grok 4.20 5 — tie and tied for 1st of 55; both are strong for retrieval and summarization across 30K+ tokens.
• structured output: GPT-5 5 vs Grok 4.20 5 — tie and tied for 1st of 54; both reliably produce JSON/schema-compliant outputs in our tests.
• persona consistency: GPT-5 5 vs Grok 4.20 5 — tie and tied for 1st of 53; both maintain character and resist injection well.
• multilingual: GPT-5 5 vs Grok 4.20 5 — tie and tied for 1st of 55; non-English quality is equivalent in our suite.
• strategic analysis: GPT-5 5 vs Grok 4.20 5 — tie and both tied for 1st of 54; both produce nuanced tradeoff reasoning with numbers.
• constrained rewriting: GPT-5 4 vs Grok 4.20 4 — tie (rank 6 of 53 for both); both handle hard character/format limits similarly.
• creative problem solving: GPT-5 4 vs Grok 4.20 4 — tie (rank 9 of 54 for both); both generate feasible non-obvious ideas at similar quality.
• classification: GPT-5 4 vs Grok 4.20 4 — tie and tied for 1st of 53; both accurate on routing/categorization tasks in our tests.
• agentic planning: GPT-5 5 vs Grok 4.20 4 — GPT-5 wins. GPT-5 is tied for 1st of 54 ("tied for 1st with 14 other models"), while Grok is rank 16 of 54; in practice GPT-5 better decomposes goals and recovers from failures in multi-step agentic flows.
• safety calibration: GPT-5 2 vs Grok 4.20 1 — GPT-5 wins. GPT-5 ranks 12 of 55 (better calibration in our tests) versus Grok at 32 of 55; GPT-5 is more likely to correctly refuse harmful requests while permitting legitimate ones in our suite. External math/coding benchmarks (Epoch AI): GPT-5 scores 73.6% on SWE-bench Verified (Epoch AI), 98.1% on MATH Level 5 (Epoch AI), and 91.4% on AIME 2025 (Epoch AI) — these place GPT-5 at rank 1 on MATH Level 5 in our rankings and show its strength on competition-style math. Grok 4.20 has no external SWE/MATH/AIME scores in the payload; treat that as missing data rather than a weakness. Net interpretation: both models are top-tier across many core capabilities (tool calling, faithfulness, long context, structured output). GPT-5’s edge is in agentic planning and safety calibration plus strong external math performance; Grok’s edge is lower output cost (material at scale) while matching GPT-5 on many tasks in our tests.

Costs from the payload (per 1,000 tokens): GPT-5 input $1.25, output $10.00; Grok 4.20 input $2.00, output $6.00. Per 1M tokens (1,000 mTok): GPT-5 = input $1,250; output $10,000. Grok 4.20 = input $2,000; output $6,000. For a 50/50 input/output split (common proxy): GPT-5 ≈ $5,625 per 1M tokens; Grok 4.20 ≈ $4,000 per 1M. Scale examples (50/50 split): 1M tokens — GPT-5 $5,625 vs Grok $4,000 (difference $1,625); 10M — GPT-5 $56,250 vs Grok $40,000 (difference $16,250); 100M — GPT-5 $562,500 vs Grok $400,000 (difference $162,500). Who should care: teams generating large volumes of output tokens (e.g., chatbots, document generation, summarization) will see the biggest savings with Grok 4.20 because GPT-5’s output rate is $10/mTok vs Grok’s $6/mTok. If output token quality or advanced planning/complex reasoning matter enough to justify higher spend, GPT-5 can be worth the premium.

Choose GPT-5 if: you need the best goal decomposition, multi-step agentic planning, stronger safety calibration, or peak math/reasoning performance (GPT-5 wins agentic planning and safety calibration in our testing and posts 98.1% on MATH Level 5, Epoch AI). Choose Grok 4.20 if: you need near-parity on tool calling, faithfulness, long-context, and structured output but at lower operational cost — Grok ≈ $4,000 vs GPT-5 ≈ $5,625 per 1M tokens on a 50/50 input/output split. Choose Grok for high-volume production where per-token output cost drives ROI; choose GPT-5 for R&D, complex automation agents, or tasks where planning and math accuracy justify the premium.