Gemini 3.1 Pro Preview vs Grok 4.3

Pricing math

Gemini 3.1 Pro Preview: $2.00/M input, $12.00/M output from Google, or $2.06/$12.36 on OpenKey ($2.00 x 1.03, $12.00 x 1.03). Grok 4.3: $1.25/M input, $2.50/M output from xAI, or $1.2875/$2.575 on OpenKey. On a 10M-input / 2M-output workload, Gemini costs $44.00 and Grok costs $17.50 — Gemini is 2.51x more expensive for that mix, driven mostly by output tokens (Gemini's completion price is 4.8x Grok's, its input price is 1.6x Grok's). If your workload is output-heavy — long generations, verbose reasoning traces — the gap widens further.

Coding and agentic performance

On artificial_analysis, Gemini 3.1 Pro Preview posts a 68.8 coding index versus Grok 4.3's 42.2 — a large gap. Intelligence index favors Gemini too, 46.5 vs 37.6. Grok flips the script on agentic_index: 24.1 vs Gemini's 21.4, a small but real edge. On Design Arena's agentic categories, Gemini leads in agenticgamedev (rank 8 vs 10), agentichtmlslides (rank 5 vs 10), godotgamedev (rank 6 vs 16), and webapps (rank 13 vs 14, close elo: 1196 vs 1194). Grok's agentic_index edge doesn't translate into Design Arena agent-category wins here — Gemini ranks better across nearly every agents category in this dataset.

Design and UI benchmarks

Gemini dominates the 'models' arena on Design Arena: svg rank 2 (elo 1347) vs Grok's rank 44 (elo 1140), asciiart rank 4 vs rank 27, uicomponent rank 8 vs rank 31, codecategories rank 18 vs rank 31, website rank 15 vs rank 31. Grok's best 'models' category is gamedev at rank 34 (elo 1242), still well behind Gemini's rank 26 (elo 1264) in the same category. If your use case involves generating SVGs, UI components, or ASCII art, the gap is not close.

Context and modality

Gemini's context window is 1,048,576 tokens against Grok's 1,000,000 — a 1.05x ratio, essentially a wash. Gemini supports max completion tokens of 65,536; Grok has no stated max_completion_tokens cap in this data. Modality differs more: Gemini accepts audio, file, image, text, and video input; Grok accepts text, image, and file only — no audio or video. If your pipeline needs to process audio or video directly, Grok 4.3 is not an option here. Both output text only.

When to pick each

Pick Gemini 3.1 Pro Preview when coding quality, design/UI generation, or multimodal input (audio/video) matters and budget is secondary. Pick Grok 4.3 when you're running high-volume agentic workloads where the 24.1 agentic_index and $17.50-per-workload cost (vs $44.00) matter more than peak coding scores. Grok's reasoning is optional (default effort 'low', can be disabled with 'none'), giving you a latency/cost lever Gemini doesn't offer since Gemini's reasoning is mandatory.

Questions

Which model is cheaper to run at scale?

Grok 4.3, by a wide margin. On a 10M-input/2M-output workload, Grok costs $17.50 versus Gemini 3.1 Pro Preview's $44.00 — Gemini's input price is 1.6x Grok's and its output price is roughly 4.8x higher ($12.00 vs $2.50 per million tokens from the provider).

Which model has the bigger context window?

Gemini 3.1 Pro Preview, but barely. It supports 1,048,576 tokens versus Grok 4.3's 1,000,000 — a context ratio of just 1.05x. For practical purposes, treat them as equivalent on context length.

Does either model handle audio or video?

Only Gemini 3.1 Pro Preview. Its input modalities include audio, file, image, text, and video. Grok 4.3 accepts text, image, and file input only — no audio or video support in this data.

Is Grok 4.3 ever ahead on benchmarks?

Yes, on artificial_analysis agentic_index: Grok scores 24.1 versus Gemini's 21.4. It's Grok's one clear numeric edge here — Gemini leads on intelligence_index (46.5 vs 37.6), coding_index (68.8 vs 42.2), and most Design Arena categories.