A rigorous, hands‑on comparison of three leading AI coding assistants—GPT‑5.1 Codex Max, Gemini 3 Pro, and Claude Opus 4.5—reveals that benchmark scores do not guarantee shipping‑ready code. The study, centered on building the Speakit MVP, shows Gemini excels in clean architecture, Opus shines in UI polish, and GPT‑5.1 offers unconventional flexibility, but all require a human in the loop for production readiness.