GPT-5.5 vs Claude Opus 4.7: Five UIs, One Honest Comparison

TLDR: Kilo ran both GPT-5.5 and Claude Opus 4.7 through five identical UI prompts (landing, dashboard, settings, sign-up, pricing) using Kilo CLI in Code mode at high reasoning, single-shot output, Tailwind via CDN. Opus produced more varied, more on-brief work with better typographic instincts; GPT-5.5 leaned on a generic modern-SaaS template and missed three prompt requirements outright. Opus is roughly 20% cheaper per output token, which makes the comparison even less flattering for the OpenAI side.

We Asked GPT-5.5 and Claude Opus 4.7 to Design 5 UIs