Gemini 3.1 Pro Preview vs Grok 4

Summary of our 12-test suite comparisons (decisive wins, losses, ties):

• Gemini wins (A): structured_output (A 5 vs B 4), creative_problem_solving (A 5 vs B 3), agentic_planning (A 5 vs B 3). In our testing Gemini's 5/5 on structured_output ties for 1st (tied with 24 others out of 54) — meaning it is top-tier for JSON schema compliance and format adherence. Creative_problem_solving (5/5, tied for 1st) indicates stronger generation of non-obvious, feasible ideas compared to Grok (3/5, rank 30 of 54).
• Grok wins (B): classification (B 4 vs A 2). In our testing Grok's classification score ties for 1st with 29 others out of 53, while Gemini ranks 51 of 53 on classification. That translates to substantially better categorization and routing reliability for Grok in production pipelines.
• Ties: strategic_analysis (both 5), constrained_rewriting (both 4), tool_calling (both 4), faithfulness (both 5), long_context (both 5), safety_calibration (both 2), persona_consistency (both 5), multilingual (both 5). Notable: both models rank tied for 1st on long_context (tied with 36 others out of 55), so both handle 30K+ token retrieval tasks at the top end of our cohort.
• External benchmark: Gemini scores 95.6% on AIME 2025 (Epoch AI) and ranks 2 of 23 on that external math benchmark — a supporting signal that Gemini is very strong on higher-difficulty reasoning/math tasks. What this means for real tasks: choose Gemini when you need robust schema compliance, multi-step planning, and creative solution generation; choose Grok when your primary need is highly accurate classification and routing. For tool-calling and long-context retrieval, both models perform similarly (4/5 and 5/5 respectively in our tests).

Pricing in the payload is per mTok: Gemini 3.1 Pro Preview charges $2 input + $12 output = $14 per mTok total; Grok 4 charges $3 input + $15 output = $18 per mTok total. At 1M tokens/month (1,000 mTok) that’s $14,000 (Gemini) vs $18,000 (Grok) — a $4,000 difference. At 10M tokens (10,000 mTok): $140,000 vs $180,000 (diff $40,000). At 100M tokens: $1,400,000 vs $1,800,000 (diff $400,000). Teams with sustained high-volume usage (10M+ tokens/month) should care deeply about the $4 per mTok gap; smaller projects or experiments (under 1M tokens/month) will see smaller absolute savings and should weigh the performance differences against budget.

Choose Gemini 3.1 Pro Preview if: you need top-tier structured output (5/5), creative problem solving (5/5), agentic planning (5/5), large context (1,048,576 window) and a lower per-mTok price ($2/$12). Ideal for apps that require strict JSON, complex planning agents, or heavy reasoning (Gemini scores 95.6% on AIME 2025, Epoch AI). Choose Grok 4 if: your primary workload is classification and routing — Grok scores 4/5 and ties for 1st in classification in our tests — or you rely on its 256k context window and the specific tooling described by the provider. Grok is the better choice for pipelines where classification accuracy outweighs schema/creative advantages. If cost at scale matters, Gemini’s lower $14/mTok combined rate is a decisive factor.