GPT-5.1 vs Grok 4

Head-to-head wins and ties (our 12-test suite): GPT-5.1 wins creative problem solving (4 vs 3) and agentic planning (4 vs 3). Grok 4 has zero outright wins. The remaining 10 tests tie: structured output (4/4), strategic analysis (5/5), constrained rewriting (4/4), tool calling (4/4), faithfulness (5/5), classification (4/4), long context (5/5), safety calibration (2/2), persona consistency (5/5), and multilingual (5/5). What that means for real tasks:

• Creative problem solving: GPT-5.1 scores 4 vs Grok 4’s 3 and ranks 9 of 54 (tied with 20 others) vs Grok’s 30 of 54 — expect GPT-5.1 to produce more non-obvious, feasible ideas in our tests.
• Agentic planning: GPT-5.1 (4, rank 16/54) outperforms Grok 4 (3, rank 42/54) on goal decomposition and recovery scenarios in our testing.
• Long-context and retrieval: both score 5 and are tied for 1st (GPT-5.1 tied with 36 others, Grok 4 the same) — both excel at 30k+ token tasks in our suite.
• Tool calling & structured outputs: both score 4 and tie (tool calling rank 18/54), indicating comparable function-selection, argument accuracy, and JSON/schema compliance in our tests.
• Faithfulness & classification: both score 5 and 4 respectively and rank tied for 1st on faithfulness (with many models), so neither has an advantage on sticking to sources or routing tasks in our benchmarks.
• Safety calibration: both score 2 and are tied (rank 12/55) — in our tests both models are conservative in safety calibration and may refuse or mishandle borderline requests similarly. External benchmarks: beyond our internal scores, GPT-5.1 scores 68 on SWE-bench Verified and 88.6 on AIME 2025 (Epoch AI). Grok 4 has no external scores in the payload. These external results support GPT-5.1’s coding and high-difficulty math performance in independent measures.

Costs are per thousand tokens (mTok). GPT-5.1: $1.25 input / $10 output per mTok. Grok 4: $3 input / $15 output per mTok. Assuming a realistic 50/50 split of input/output tokens, combined cost per mTok is $11.25 for GPT-5.1 and $18.00 for Grok 4. Monthly totals at that 50/50 split:

• 1M tokens (1,000 mTok): GPT-5.1 = $5,625; Grok 4 = $9,000 (difference $3,375).
• 10M tokens: GPT-5.1 = $56,250; Grok 4 = $90,000 (difference $33,750).
• 100M tokens: GPT-5.1 = $562,500; Grok 4 = $900,000 (difference $337,500). Who should care: high-volume applications and startups with tight margins — the per-mTok gap compounds quickly. Teams that value Grok 4’s specific parameter options or xai integrations may accept the ~60% higher combined token cost ($18 vs $11.25) for their workflows.

Choose GPT-5.1 if: you need the best creative and planning performance from these two models (creative problem solving 4 vs 3; agentic planning 4 vs 3), want much lower token costs ($1.25/$10 vs $3/$15 per mTok), or require the largest context window (400,000 tokens). Ideal for startups and production APIs where cost-per-token and creative/agentic capability matter. Choose Grok 4 if: you need xai’s parameter surface (temperature, top_p, top_logprobs) or its 'uses_reasoning_tokens' behavior, and you accept a higher token bill for parity on long-context, faithfulness, classification, and tool calling. Grok 4 ties on many categories, so pick it when those specific integration or parameter features are decisive.