Grok 4.20 (Reasoning) vs GPT-5.5
Side-by-side comparison across metrics, pricing, and overall score — every value traced to a source.
Verdict: GPT-5.5 ranks highest overall (#3) with a score of 52.5.
The best choice still depends on which metrics matter for your workload — per-metric winners are marked below.
What the numbers hide
Computed from the published values below — no estimates, no generated claims.
Fragile verdict
The overall winner flips to GPT-5.5 if Context Window is weighted at 30% (it counts for 18% today). If context window drives your decision, the ranking above may not be your ranking.
Fragile verdict
The overall winner flips to GPT-5.5 if Output Price is weighted at 5% (it counts for 18% today). If output price drives your decision, the ranking above may not be your ranking.
Real tradeoff
Grok 4.20 (Reasoning) clearly beats GPT-5.5 on Input Price but clearly loses on Context Window — this pair is a priorities question, not a quality question.
What nobody reports
SWE-Bench Pro Score (1 of 2 missing) — the questions worth asking vendors directly.
AI hot take
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| Metric | Grok 4.20 (Reasoning)xAI | GPT-5.5OpenAI |
|---|---|---|
| Overall OptiSift Score | 31.6#12 | 52.5#3 |
| Input Price | $1.25 | $5 |
| Output Price | $2.5 | $30 |
| Cache Read Price | $0.2 | $0.5 |
| Context Window | 1M | 1.1M |
| Max Output Tokens | 30K | 128K |
| SWE-Bench Pro Score | — | 58.6% |
| Tool Calling | Yes | Yes |
| Extended Reasoning | Yes | Yes |
About these models
#12Grok 4.20 (Reasoning)
xAI
Grok 4.20 (Reasoning) is xAI's reasoning-capable model: $1.25/$2.50 per 1M input/output tokens, 1M token context window.
#3GPT-5.5
OpenAI
GPT-5.5 is OpenAI's reasoning-capable model: $5/$30 per 1M input/output tokens, 1.1M token context window, 58.6% on SWE-Bench Pro.