Gemini 3.1 Pro Preview vs Grok 3

Test-by-test summary (scores on our 1–5 scale). Gemini 3.1 Pro Preview wins: constrained_rewriting 4 vs Grok 3's 3 — Gemini ranks 6 of 53 on that test (tied with 24 others), indicating stronger compression/character-limit rewriting. Creative_problem_solving 5 vs 3 — Gemini is tied for 1st (tied with 7 others out of 54), so it produces more non-obvious, feasible ideas in our tests. Grok 3 wins classification 4 vs Gemini's 2 — Grok is tied for 1st (tied with 29 others out of 53), while Gemini ranks 51 of 53, so Grok is clearly preferable for routing and labeling tasks. The following tests tie (no clear winner): structured_output 5/5 (both tied for 1st), strategic_analysis 5/5 (both tied for 1st), tool_calling 4/4 (both rank 18 of 54), faithfulness 5/5 (both tied for 1st), long_context 5/5 (both tied for 1st), safety_calibration 2/2 (both rank 12 of 55), persona_consistency 5/5 (both tied for 1st), agentic_planning 5/5 (both tied for 1st), and multilingual 5/5 (both tied for 1st). Notable external benchmark: on AIME 2025 (Epoch AI) Gemini scores 95.6% and ranks 2 of 23, which supports its strong math/complex-reasoning performance in our evaluation; Grok 3 has no AIME score in the payload. In practice: Gemini is the higher-performing choice for creative problem solving, long-context reasoning, and constrained rewriting (including structured outputs), while Grok 3 is the clear winner when classification accuracy is the primary requirement.

Costs are quoted per mTok (per 1,000 tokens). Gemini 3.1 Pro Preview: input $2/mTok, output $12/mTok. Grok 3: input $3/mTok, output $15/mTok. Per 1M tokens (1,000 mTok): Gemini input = $2,000; output = $12,000. Grok input = $3,000; output = $15,000. If you split tokens 50/50 input/output (common for chat+completion), per 1M tokens Gemini ≈ $7,000 vs Grok ≈ $9,000 (Gemini saves $2,000). At 10M tokens/month (50/50) Gemini ≈ $70,000 vs Grok ≈ $90,000 (saves $20,000). At 100M tokens/month (50/50) Gemini ≈ $700,000 vs Grok ≈ $900,000 (saves $200,000). High-volume deployments, cost-sensitive products, and startups should care about this gap; teams that need Grok 3's classification edge may accept the higher spend.

Choose Gemini 3.1 Pro Preview if you need top-tier creative problem solving, long-context reasoning, reliable structured outputs, or better constrained-rewriting performance — it wins 2 of 3 decisive tests and posts 95.6% on AIME 2025 (Epoch AI), and it costs less per token (input $2, output $12). Choose Grok 3 if classification/routing is your primary need (Grok 3 scores 4 vs Gemini's 2) and you accept the higher price (input $3, output $15) for that advantage.