Gemini 3 vs. Claude Opus 4.5 vs. GPT-5.1 Codex: Which AI model is the best designer?

What It Covers

Claire Vo tests three leading AI coding models—Gemini 3 Pro, Claude Opus 4.5, and GPT-5.1 Codex—by having each redesign an existing blog page to determine which performs best at front-end design work.

Key Questions Answered

• •Model-specific workflows: Opus 4.5 creates structured to-do lists before coding (redesign listing page, improve layout, enhance post display, add SEO), while Gemini 3 executes immediately without planning steps. This planning capability produces 20-30% better design details and functional improvements across components.
• •Design quality hierarchy: Opus 4.5 delivers superior results with asset selection from existing repositories, placeholder images for missing content, hover animations with call-to-action arrows, and reading time estimates. Gemini 3 produces serviceable designs with glass morphism cards and hero sections but lacks refinement in spacing and asset handling.
• •SEO implementation differences: Gemini 3 adds JSON-LD schema, breadcrumbs, semantic HTML, and related articles to individual posts. Opus 4.5 implements metadata, Open Graph tags, and structured data but skips JSON-LD. Codex 5.1 provides minimal SEO with basic metadata and schema.org embedding only.
• •Model specialization strategy: Use different models for different workflow stages rather than one model for everything. Opus 4.5 excels at front-end design, Codex 5.1 performs better on back-end engineering tasks, and Gemini 3 handles mid-tier design work requiring less detailed planning and implementation steps.