Quick Take

Released just one week apart in April 2026, Grok 4.3 (medium) and GPT-5.5 (xhigh) represent the latest offerings from xAI and OpenAI, respectively. While Grok 4.3 focuses on high-speed, affordable utility, GPT-5.5 positions itself as a premium, high-intelligence powerhouse.

Benchmark Read

GPT-5.5 consistently outperforms Grok 4.3 across key metrics. GPT-5.5 holds an Intelligence index of 60.2 compared to Grok 4.3’s 48.8. The gap is even more pronounced in coding, where GPT-5.5 scores 59.1 against Grok 4.3’s 35.1.

In specific benchmarks, GPT-5.5 leads in:

• GPQA: 0.935 (vs 0.89)
• HLE: 0.443 (vs 0.281)
• SciCode: 0.561 (vs 0.446)
• TerminalBench Hard: 0.606 (vs 0.303)
• TAU2: 0.938 (vs 0.912)

Grok 4.3 does show a slight advantage in IFBench, scoring 0.833 compared to GPT-5.5’s 0.758. Math index data remains unknown for both models.

Cost and Speed

Grok 4.3 is significantly more economical, with a blended price of $1.56/1M tokens, compared to the $11.25/1M blended cost for GPT-5.5.

Performance metrics favor Grok 4.3 for real-time applications:

• Output Speed: Grok 4.3 hits 106.798 tok/s, while GPT-5.5 reaches 65.098 tok/s.
• Time to First Token: Grok 4.3 is much faster at 30.395s, compared to 69.69s for GPT-5.5.

Best Fit

Grok 4.3 is the ideal choice for developers and businesses requiring high-throughput, low-latency interactions where cost management is a priority. GPT-5.5 is best suited for complex reasoning tasks, advanced software development, and scenarios where the highest possible intelligence index is required, regardless of the increased operational cost.