GPT-5.5 Instant vs Grok 4.3
GPT-5.5 Instant 
Grok 4.3 Verdict
- GPT-5.5 Instant and Grok 4.3 (medium) are level on quality (60.5 vs 60.7).
- GPT-5.5 Instant is stronger in agents & tools, coding, composite, human preference, maths, reasoning.
- Grok 4.3 (medium) is stronger in instruction following, knowledge, long context, multimodal.
- Grok 4.3 (medium) is 7.2× cheaper ($1.56 vs $11.25 per 1M blended).
| Metric | GPT-5.5 Instant | Grok 4.3 (medium) |
|---|---|---|
| BenchLeader Index | 60.5 | 60.7 |
| Agents & tools score | 70.7 | 60.1 |
| Coding score | 61.1 | – |
| Composite score | 62.9 | 60.3 |
| Human preference score | 67.5 | – |
| Instruction following score | 69.8 | 80.0 |
| Knowledge score | 69.4 | 72.1 |
| Long context score | 61.4 | 64.0 |
| Maths score | 42.5 | – |
| Multimodal score | 59.7 | 60.2 |
| Reasoning score | 62.6 | – |
| Blended price $/M | $11.25 | $1.56 |
| Output speed | 129 tok/s | 112 tok/s |
| Time to first answer | 16.8 s | 12.1 s |
| Context window | 400k | 1M |
| GPQA Diamond | 82.5% | – |
| FrontierMath Tiers 1–3 | 26.3% | – |
| FrontierMath Tier 4 | 2.4% | – |
| OTIS Mock AIME | 68.1% | – |
| SciCode | 48.6% | – |
| Epoch Capabilities Index | 142.5 | – |
| LMArena Text | 1474 | – |
| LMArena Hard Prompts | 1491 | – |
| LMArena Coding | 1514 | – |
| LMArena Vision | 1251 | – |
| AA Intelligence Index | 26.8 | 24.8 |
| IFBench | 71.5% | 83.3% |
| AA-LCR | 70.0% | 75.0% |
| MMMU-Pro | – | 75.8% |
| AA-Omniscience | 11.2 | 16.7 |
| Terminal-Bench Hard | 42.4% | 30.3% |
| GPQA Diamond (AA) | 84.7% | 89.0% |
| Humanity's Last Exam (AA) | 21.6% | 30.0% |
| SciCode (AA) | 52.5% | – |
| τ²-Bench Telecom (AA) | 49.4% | 91.2% |
Data as of 2026-09-10. Best configuration of each model; every score links to its source on the model pages.
GPT-5.5 Instant vs Grok 4.3: questions
- Is GPT-5.5 Instant better than Grok 4.3?
- GPT-5.5 Instant and Grok 4.3 (medium) are level on quality (60.5 vs 60.7). The BenchLeader Index combines every independent quality benchmark; Grok 4.3 (medium) is ahead overall as of 2026-09-10, but check the category scores for your use.
- Is GPT-5.5 Instant better than Grok 4.3 for agentic tasks?
- GPT-5.5 Instant scores higher in agentic tasks (71 vs 60 on the category index, where 50 is average).
- Which is cheaper, GPT-5.5 Instant or Grok 4.3?
- Grok 4.3 is cheaper: $1.56 against $11.25 per million tokens, blended at three input tokens per output token.
- Which is faster, GPT-5.5 Instant or Grok 4.3?
- GPT-5.5 Instant streams faster: 129 against 112 output tokens per second.
- Which has the larger context window?
- Grok 4.3 accepts more context: 1M against 400k tokens.