Proprietary LLM Comparison 2026 Claude Opus 4.6, GPT-5.4, Gemini 3.1 Pro, Grok 4.20 — benchmarks, pricing, and real-world performance
All four frontier proprietary models now score above 72% on SWE-bench Verified, but they diverge sharply on price, context window, and specialised strengths. Gemini 3.1 Pro leads reasoning benchmarks (94.3% GPQA Diamond) and offers the cheapest output pricing at $12/1M tokens for prompts under 200K. Claude Opus 4.6 leads on SWE-bench (80.8%) and agentic coding. GPT-5.4 introduces native computer-use — the first general-purpose model with built-in GUI and browser control. Grok 4.20 offers the largest context window (2M tokens) at the lowest output price ($6/1M) with live web access via X.
Closed-Source Frontier LLMs
API-only models from the major AI labs as of April 2026, evaluated across pricing, benchmarks, and real-world strengths.
| Dimension | Claude Opus 4.6 | GPT-5.4 | Gemini 3.1 Pro | Grok 4.20 |
|---|---|---|---|---|
| Context window | 1M tokens | 272K (standard) — up to 1M via extended config | 1M tokens | 2M tokens |
| Input price (per 1M tokens) | $5.00 | $2.50 (≤272K) / $5.00 (>272K) | $2.00 (≤200K) / $4.00 (>200K) | $2.00 |
| Output price (per 1M tokens) | $25.00 | $15.00 | $12.00 (≤200K) / $18.00 (>200K) | $6.00 |
| SWE-bench Verified | 80.8% | ~74.9% | ~80.6% (variance across evaluators — some report 63.8%) | 72–75% (Grok 4 Code; not yet confirmed by benchmark org) |
| Reasoning (GPQA Diamond) | 91.3% | 92.0% | 94.3% — highest of the four | ~87.5% |
| Multimodal input | Text + images | Text + images + native computer-use (GUI / browser control) | Text + images + audio + video | Text + images + video (via grok-imagine suite) |
| Real-time data access | No — knowledge cutoff Aug 2025 | No — static training data | No — static training data | Yes — live X/web data access built in |
| API availability | Anthropic API, AWS Bedrock, Google Vertex AI | OpenAI API, Azure OpenAI | Google AI API, Vertex AI (preview status as of Apr 2026) | xAI API only |
| Best for | Autonomous coding agents, large-context document analysis, agentic workflows | Computer-use automation, broad ecosystem, voice/audio applications | Reasoning benchmarks, multimodal tasks, cost-sensitive long-context inference | Real-time data apps, lowest output cost, 2M-token analysis |
When to choose each
Claude Opus 4.6
- Autonomous coding via Claude Code (80.8% SWE-bench Verified — highest of the four)
- 1M-context analysis of large codebases, contracts, or research papers
- Enterprise agentic workflows needing careful permission controls
- Teams using AWS Bedrock or Google Vertex AI infrastructure
GPT-5.4
- Computer-use automation — the only general-purpose model with native screen/browser control
- Teams deep in the OpenAI or Azure OpenAI ecosystem
- Voice and audio applications via GPT-5.4 audio input
- Broadest third-party plugin and integration ecosystem
Gemini 3.1 Pro
- Projects needing the highest reasoning accuracy (94.3% GPQA Diamond)
- Multimodal analysis combining images, audio, and video in one prompt
- Cost-sensitive inference — cheapest output price ($12/1M) for prompts under 200K
- Google Workspace integration and Vertex AI deployment
Grok 4.20
- Applications needing live social media data or real-time web context
- Largest context window (2M tokens) at the lowest output cost ($6/1M)
- Social listening, market monitoring, and trend analysis via X platform
- Multi-agent tasks using Grok 4.20 Heavy (16-agent specialist system)
Our verdict
No proprietary model wins across all dimensions in April 2026. Gemini 3.1 Pro leads on reasoning (94.3% GPQA) and offers the lowest output price at $12/1M. Claude Opus 4.6 leads autonomous coding at 80.8% SWE-bench. GPT-5.4 uniquely offers native computer-use. Grok 4.20 has the largest context window (2M tokens), lowest output cost ($6/1M), and live web/X data access. Choose based on primary workload: coding → Claude, reasoning/multimodal → Gemini, computer-use → GPT, real-time data → Grok.
Sources & References
- 01Anthropic Model Docs — Claude Opus 4.6
Official model specifications, pricing, and context window
- 02OpenAI — Introducing GPT-5.4
Official announcement; March 5, 2026
- 03Google AI — Gemini 3.1 Pro Models Page
Released February 19, 2026; preview status
- 04Google AI — Gemini API Pricing
Official tiered pricing for Gemini 3.1 Pro
- 05xAI API — Models and Pricing
Grok 4.20: $2.00/$6.00 per 1M tokens, 2M context window
- 06SWE-bench Leaderboard
Canonical benchmark for autonomous software engineering tasks
- 07Artificial Analysis — LLM Benchmarks
Independent quality, speed, and price comparisons across providers
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