Grok 4.1 Fast vs Qwen2.5 72B Instruct

Grok 4.1 Fast

xAI

Grok 4.1 Fast, released by xAI in November 2025, is a fast-response variant from the Grok 4 family featuring a 2M token context window designed for high-throughput applications. It omits thinking tokens for immediate responses, reducing latency while maintaining strong output quality. Grok 4.1 Fast targets production APIs, real-time assistants, and cost-sensitive applications requiring long-context understanding at high volume.

Alibaba / Qwen

Qwen2.5-72B-Instruct is the flagship of Alibaba's Qwen2.5 series, a 72-billion-parameter open-weight model released in September 2024 after training on 18 trillion tokens spanning code, mathematics, and multilingual text. It offers strong generalist performance across coding, instruction-following, and structured reasoning while remaining fully open-weight under Apache 2.0 — a combination that made it a widely referenced model in open-source evaluations and community benchmarking. The 128K context window and built-in structured output support made it a common choice for document analysis and multi-step agentic pipeline development.