Quick Take

Released in late April 2026, Grok 4.3 (low) and GPT-5.5 (xhigh) target different segments of the AI market. Grok 4.3 emphasizes speed and affordability, whereas GPT-5.5 positions itself as a high-intelligence powerhouse designed for complex problem-solving.

Benchmark Read

GPT-5.5 (xhigh) consistently outperforms Grok 4.3 (low) across all measured metrics.

• Intelligence & Coding: GPT-5.5 leads with an Intelligence Index of 60.2 and a Coding Index of 59.1, compared to Grok 4.3’s 43.9 and 31.6, respectively.
• Reasoning & Accuracy: GPT-5.5 demonstrates higher proficiency in specialized benchmarks, scoring 0.935 on GPQA and 0.606 on TerminalBench Hard, while Grok 4.3 scores 0.843 and 0.265 in those same categories.
• Instruction Following: Interestingly, Grok 4.3 (0.809) slightly edges out GPT-5.5 (0.758) in IFBench, suggesting it may be more reliable for specific instruction-following tasks despite lower overall intelligence.

Cost and Speed

There is a stark contrast in operational efficiency between the two models:

• Pricing: Grok 4.3 is significantly cheaper, with a blended cost of $1.56/1M tokens, compared to GPT-5.5’s $11.25/1M tokens. GPT-5.5’s output cost is particularly high at $30.00/1M tokens.
• Performance: Grok 4.3 is optimized for speed, delivering a time-to-first-token of 13.852s and an output speed of 80.284 tok/s. GPT-5.5 is notably slower, with a time-to-first-token of 71.023s and an output speed of 65.375 tok/s.

Best Fit

Grok 4.3 (low) is best suited for high-volume, cost-sensitive applications where rapid response times are critical. Its lower intelligence index is offset by its efficiency. GPT-5.5 (xhigh) is the ideal candidate for complex, high-stakes reasoning and coding projects where accuracy and depth of intelligence are more important than immediate response times or budget constraints.