GPT-5.5 is the stronger model on reasoning and complex tasks. Grok 4.3 is cheaper, faster, and has a dramatically larger context window. For most practical use cases, GPT-5.5 edges out on quality; for cost-sensitive or latency-sensitive applications, Grok 4.3 offers real advantages at a fraction of the API price.
Specs side by side
GPT-5.5Grok 4.3LabOpenAIxAIContext window128K tokens1M tokensInput price$5.00/M tokens$1.25/M tokensOutput price$30.00/M tokens$2.50/M tokensSpeed~50-80 tok/s~207 tok/sSWE-bench Verified82.7%Not publishedAI Analysis Index60.253Consumer planChatGPT Plus ($20/mo)SuperGrok ($30/mo)
The key differences
Price: Grok 4.3 costs 75% less on input and 92% less on output. At scale, this isn't a marginal difference — running one million output tokens through GPT-5.5 costs $30, through Grok 4.3 it costs $2.50.
Context window: Grok's 1M tokens vs GPT-5.5's 128K. For processing large codebases, long documents, or data-heavy tasks, Grok's context capacity is a real operational advantage.
Speed: 207 tokens per second vs GPT-5.5's 50-80. Grok is 2-4x faster. For real-time applications, voice interfaces, or interactive tools, this latency difference matters.
Reasoning quality: GPT-5.5 scores 60.2 on the Artificial Analysis Intelligence Index vs Grok 4.3 at 53. For complex multi-step reasoning, GPT-5.5 is the stronger model. Grok 4.3 improved a lot over its predecessor but hasn't closed the gap with the top OpenAI and Anthropic models.
Hallucination rate: Grok 4.3 holds the record at 78% non-hallucination on the Omniscience benchmark — above average for its tier. GPT-5.5 also performs well here, but Grok's always-on reasoning (which can't be disabled) may contribute to its factual accuracy.
Who should use Grok 4.3
Grok 4.3 is the right pick when: - You need to process very long documents or codebases (1M context) - Inference cost at scale is a significant constraint - Response speed is a product requirement (real-time chat, voice) - General tasks don't require frontier-level reasoning - You're already paying for X Premium+ and want model access bundled
Who should use GPT-5.5
GPT-5.5 is the right pick when: - You need top-tier reasoning on complex multi-step tasks - You rely on OpenAI's broader ecosystem (Sora, DALL-E, Assistants API) - Quality matters more than cost in your specific workflow - You're building on the ChatGPT platform with plugins or custom GPTs
On consumer pricing
This is the quirk: Grok 4.3 is cheaper at the API level but more expensive as a consumer subscription. SuperGrok costs $30/month; ChatGPT Plus costs $20/month. If you're using consumer products rather than the API, GPT-5.5 via ChatGPT Plus is better value per dollar.
The API economics flip this entirely — Grok's $1.25/$2.50 per million tokens versus GPT-5.5's $5.00/$30.00 makes Grok dramatically cheaper at any serious usage volume.
