Claude Opus 5.5 vs GPT-6 Astra vs Grok 4.7: Which Frontier AI Model Should You Choose?
Three frontier models shipped within three weeks of each other. We compare pricing, benchmarks, and ideal workloads for each.
3 min read
September 2026 delivered three frontier AI models within three weeks: OpenAI's GPT-6 Astra (September 3), xAI's Grok 4.7 (September 21), and Anthropic's Claude Opus 5.5 (September 22). All three target teams running coding agents, long-document analysis, and multi-hour autonomous tasks — but they differ sharply on price, performance, and specialization.
Quick Verdict
- Claude Opus 5.5 ($4/$20 per million tokens): Best all-rounder. Leads Artificial Analysis Intelligence Index at 58.
- GPT-6 Astra ($10/$50 per million tokens): Wins on scientific and terminal work. Uses fewest tokens per task.
- Grok 4.7 ($2/$6 per million tokens): Cheapest output tokens. Good for cost-sensitive coding at the expense of speed.
Pricing Breakdown
| Model | Input/1M tokens | Output/1M tokens | Context Window |
|---|---|---|---|
| Opus 5.5 | $4 | $20 | 1M tokens |
| GPT-6 Astra | $10 | $50 | Large |
| Grok 4.7 | $2 | $6 | 500K tokens |
Astra's output tokens cost 8x Grok's. Opus sits in the middle. For teams processing millions of output tokens monthly, this spread determines total spend more than benchmark scores.
Benchmark Comparison
Artificial Analysis v4.3.2 independent rankings:
| Metric | Opus 5.5 | GPT-6 Astra | Grok 4.7 |
|---|---|---|---|
| Intelligence Index | 58 (#1) | 53 | 46 (#21) |
| Output tokens to run index | 260M | 60M | 240M |
| Cost to run full index | $8,708 | $5,324 | $4,967 |
| Output speed | TBD | 60.7 tok/s | 39.2 tok/s |
Astra uses the fewest tokens per evaluation — meaning it is more efficient even at higher per-token prices. Grok's low list price nearly matches Astra's total suite cost despite scoring lower on intelligence.
Best For Each Workload
Choose Opus 5.5 if:
- You need the highest benchmark scores for coding agents
- Long-context document work is your primary use case
- Alignment and safety safeguards matter for your application domain
Choose GPT-6 Astra if:
- Scientific research and terminal-based workflows dominate
- Token efficiency matters more than per-token price
- You need OpenAI's ecosystem integration (ChatGPT, Codex, API)
Choose Grok 4.7 if:
- Budget is the primary constraint
- You can tolerate slower, more verbose output
- Your workloads are coding-focused rather than general reasoning
The September 22 Complication
OpenAI also launched GPT-6 Sol on September 22 at $2/$10 per million tokens, directly competing with Opus 5.5 at half the price. Anthropic claims Opus 5.5 still leads on intelligence; OpenAI claims Sol wins on cost-per-task.
Independent head-to-head testing on identical workloads remains the only reliable way to choose. Vendor benchmarks are marketing until verified.
Our Recommendation
Start with Opus 5.5 for quality-critical work and Grok 4.7 for high-volume, cost-sensitive tasks. Evaluate Astra for scientific and research workloads where token efficiency compounds. Test GPT-6 Sol as a potential Opus 5.5 replacement if independent benchmarks confirm OpenAI's cost-per-task claims.
Revisit this comparison in 30 days when third-party evaluators publish Sol vs. Opus 5.5 results.
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