GPT-5 vs Grok Code Fast 1

Across our 12-test suite GPT-5 wins 9 tests, Grok Code Fast 1 wins 0, and they tie on 3. Detailed walk-through: 1) Tool calling — GPT-5: 5 vs Grok: 4. GPT-5 is tied for 1st of 54 models (tied with 16 others), indicating best-in-class function selection and argument accuracy for integrations. 2) Long context — GPT-5: 5 vs Grok: 4. GPT-5 ties for 1st of 55 (36 others), meaning stronger retrieval and coherence at 30K+ token contexts; Grok ranks 38 of 55. 3) Structured output — GPT-5: 5 (tied for 1st of 54) vs Grok: 4 (rank 26 of 54); GPT-5 is more reliable at JSON/schema compliance. 4) Strategic analysis — GPT-5: 5 (tied for 1st of 54) vs Grok: 3 (rank 36); GPT-5 delivers better nuanced tradeoff reasoning with numbers. 5) Faithfulness — GPT-5: 5 (tied for 1st of 55) vs Grok: 4 (rank 34); GPT-5 is less likely to hallucinate. 6) Persona consistency — GPT-5: 5 (tied for 1st of 53) vs Grok: 4; GPT-5 better maintains character and resists injection. 7) Multilingual — GPT-5: 5 (tied for 1st of 55) vs Grok: 4; GPT-5 gives higher non‑English parity. 8) Creative problem solving — GPT-5: 4 (rank 9 of 54) vs Grok: 3 (rank 30); GPT-5 yields more specific feasible ideas. 9) Constrained rewriting — GPT-5: 4 (rank 6 of 53) vs Grok: 3 (rank 31); GPT-5 compresses to hard limits better. 10) Classification — both 4 and tied for 1st (GPT-5 tied with 29 others; Grok tied with 29 others) — both are equally good for routing/categorization. 11) Safety calibration — both score 2 (rank 12 of 55 tie) — neither is a safety leader in our tests. 12) Agentic planning — both score 5 and tie for 1st (tied with 14 others) — both decompose goals effectively. External benchmarks (Epoch AI): GPT-5 scores 73.6% on SWE-bench Verified, 98.1% on MATH Level 5 (rank 1 of 14, sole holder), and 91.4% on AIME 2025 (rank 6 of 23). Grok has no external benchmark scores in the payload to supplement our internal tests. In short, GPT-5 wins on practically every capability that affects correctness, long-context reasoning, and complex code/math; Grok is close on planning and classification but sits lower on tool calling, long context, and faithfulness.

Costs are per 1k tokens (mTok). GPT-5 input $1.25 + output $10.00; Grok Code Fast 1 input $0.20 + output $1.50. Assuming a 50/50 split of input/output tokens, cost per 1M tokens/month: GPT-5 = $5,625; Grok = $850. At 10M: GPT-5 = $56,250 vs Grok = $8,500. At 100M: GPT-5 = $562,500 vs Grok = $85,000. The payload shows a price ratio of ~6.67× (GPT-5 is ~6.67 times more expensive). If your workload is output‑heavy (more generated tokens), the absolute gap widens (e.g., with 80% output the per‑1M cost rises to ~$8,250 for GPT-5 vs ~$1,240 for Grok). Teams running millions of tokens/month or tight margin products should care — Grok materially reduces monthly AI spend; GPT-5 demands a much larger budget but buys higher benchmark performance.

Choose GPT-5 if you need the highest accuracy for complex instruction following, long‑context retrieval, math-heavy problems (MATH Level 5: 98.1%) or mission‑critical code/tool calling — you’re paying a ~6.67× premium for that quality. Choose Grok Code Fast 1 if you must minimize per‑token cost at scale, need an economical agentic coding model that exposes reasoning traces and ties with GPT-5 on agentic planning and classification, or have latency/cost constraints that make GPT-5 unaffordable.