Foundation Model APIs (LLM & Multimodal) · Head to head
Anthropic vs xAI
Both products compete in Foundation Model APIs (LLM & Multimodal). Foundation model APIs sell metered access to frontier large-language and multimodal models: OpenAI (GPT-5.x), Anthropic (Claude Opus/Sonnet/Haiku), Google (Gemini 3.x), Mistral, and xAI (Grok), plus resellers and gateways (AWS Bedrock, Azure OpenAI, OpenRouter) that pass through provider pricing. Flagship rates run roughly $1-10 per million input tokens and $10-50 per million output tokens, with cheap commodity tiers (flash/mini/nano) at $0.10-0.50. This is the layer every AI chat, agent, copilot, and generation feature is built on. Here are the facts the B4 Index maintains on each, side by side.
The two files, side by side
The decision underneath the comparison
Choosing between Anthropic and xAI assumes you're buying Foundation Model APIs (LLM & Multimodal) at all. That's the prior question, and the B4 Index scores it on two axes: how much Foundation Model APIs (LLM & Multimodal) differentiates you, and how far AI has come at building it. Read the build-versus-buy considerations for Foundation Model APIs (LLM & Multimodal) before you shortlist either product.