GPT-5.2 vs Gemini 3 Pro for Web Development: Which AI Generates Better UI Code?

December 2025 marks a turning point in the AI coding wars. OpenAI just dropped GPT-5.2 on December 11th, while Google's Gemini 3 Pro has been dominating benchmarks since November. For developers generating UI code—React components, landing pages, dashboards—which model actually delivers better results? We put them head-to-head.

The Contenders: GPT-5.2 vs Gemini 3 Pro

Both models represent a massive leap from their predecessors. Here's what you're working with:

ChatGPT with GPT-5.2 (OpenAI)

• Released: December 11, 2025
• Variants: Instant (fast), Thinking (complex tasks), Pro (maximum accuracy)
• Context window: 256K tokens
• Key strength: Produces high-quality code, generates front-end UI with minimal prompting
• Available in: ChatGPT Plus/Pro, API, Cursor, many IDEs
• Pricing: $20/month (Plus), $200/month (Pro), API usage-based

Google Gemini 3 Pro

• Released: November 18, 2025
• Variants: Gemini 3 Pro, Gemini 3 Deep Think
• Context window: 1M tokens (!)
• Key strength: #1 on LMArena (1501 Elo), best-in-class multimodal, "vibe-coding" capabilities
• Benchmark: Beat GPT-5 Pro on Humanity's Last Exam (41% vs 31.64%)
• Available in: Gemini app, AI Studio, Vertex AI
• Pricing: Free tier, $20/month (Advanced)

Test 1: Simple React Component

Let's start with a basic test. We asked both AIs to generate a button component:

Create a React button component with Tailwind CSS that has:
- Primary, secondary, and ghost variants
- Small, medium, and large sizes
- Loading state with spinner
- Disabled state
- Icon support (left and right)

GPT-5.2 (Thinking mode) Output

Strengths:

• Impeccable TypeScript with proper generics
• Uses modern cva (class-variance-authority) pattern automatically
• Complete accessibility (ARIA, keyboard navigation)
• Includes Storybook stories without being asked

Weaknesses:

• Can be over-engineered for simple use cases
• Thinking mode adds latency (~5-10s)

Gemini 3 Pro Output

Strengths:

• Extremely fast generation
• Clean, readable code structure
• Excellent default styling choices
• Often includes interactive preview suggestions

Weaknesses:

• TypeScript types sometimes need refinement
• Occasionally misses accessibility attributes

Winner: GPT-5.2 — More polished and production-ready, especially with Thinking mode.

Test 2: Complete Landing Page

Now for a more complex challenge:

Create a SaaS landing page with:
- Hero section with gradient background
- Features grid (6 features with icons)
- Pricing section (3 tiers)
- Testimonials carousel
- FAQ accordion
- Footer with newsletter signup
- Dark mode support
- Fully responsive

Results

Winner: Gemini 3 Pro — Here's the thing: even with identical prompts, Gemini's output just looks better. We can't fully explain it, but the spacing, colors, and overall aesthetic consistently outshine GPT-5.2. It's not about benchmarks—it's about the end result.

Test 3: Dashboard with Data Visualization

Let's test something more technical:

Create an analytics dashboard with:
- Sidebar navigation with collapsible menu
- Header with search and user dropdown
- Stats cards showing KPIs
- Line chart for revenue over time
- Bar chart for user acquisition
- Recent activity feed
- Data table with sorting and pagination

Results

GPT-5.2:

• Generated complete dashboard with Recharts integration
• Proper state management with React Query
• Clean component separation and folder structure
• Realistic mock data with TypeScript types
• Dark mode toggle built-in

Gemini 3 Pro:

• Excellent overall architecture
• 1M token context = remembers entire dashboard across iterations
• Better at generating interactive "generative interfaces"
• Suggests D3.js for complex visualizations when appropriate
• Can analyze existing dashboard screenshots and match the style

Winner: Gemini 3 Pro — The massive context window and multimodal capabilities shine for complex dashboards.

Test 4: Following Design System

Can these AIs follow an existing design system?

Using this design system:
- Primary color: #6366f1 (indigo)
- Font: Inter
- Border radius: 12px for cards, 8px for buttons
- Shadows: subtle, using rgba(0,0,0,0.1)

Create a user profile card component that matches this system.

Results

GPT-5.2: Exceptional at adhering to design tokens. Uses CSS variables by default. Maintains perfect consistency across all generated components.

Gemini 3 Pro: Much improved over previous versions. Can now import and reference your existing Tailwind config. The "vibe-coding" feature sometimes adds creative flourishes you didn't ask for.

Winner: GPT-5.2 — More predictable and precise when following strict specifications.

Test 5: Debugging and Iteration

How do they handle follow-up requests?

The button doesn't show the loading spinner correctly on Safari. 
Also, add a ripple effect on click like Material UI.

Results

GPT-5.2:

• Instantly identifies Safari-specific CSS issues
• Provides working ripple effect with proper cleanup
• 256K context handles most projects well
• "Thinking" mode shows reasoning steps for complex bugs

Gemini 3 Pro:

• 1M token context = your entire codebase in memory
• Can analyze multiple files simultaneously for bug sources
• "Deep Think" mode for particularly tricky issues
• Provides multiple solution approaches with trade-offs

Winner: Gemini 3 Pro — The 1M token context is unbeatable for large-scale debugging.

Head-to-Head Summary (December 2025)

Practical Recommendations

Use Gemini 3 Pro When:

• You want prettier results with less effort — Works great even with lazy prompts
• Building landing pages, marketing sites, any user-facing UI
• You don't want to spend 20 minutes crafting the perfect prompt
• Working on large codebases (1M tokens = entire project)
• Analyzing screenshots/mockups to generate matching code
• You care more about how it looks than technical perfection

Use GPT-5.2 When:

• Writing business logic — More reliable and predictable
• Need strict TypeScript type safety
• Accessibility compliance is critical (WCAG)
• Following exact specifications without creative deviations
• Working within Cursor or v0 (native integration)
• You need the output to be technically correct, not pretty

The Pro Move: Use Both

Top developers in December 2025 are combining both:

1. Gemini 3 for design: Generate beautiful UI, creative layouts
2. GPT-5.2 for logic: Add business logic, API calls, state management
3. Gemini 3 for review: Visual polish, design consistency check
4. GPT-5.2 for accessibility: ARIA labels, keyboard nav, type safety

The IDE Factor: Where You Use Them Matters

Raw model performance is only part of the story. Integration matters:

Cursor (GPT-5.2 + Claude)

• Best-in-class IDE integration with GPT-5.2
• Understands your entire codebase
• Inline completions and chat
• Agent mode for complex refactoring
• Explore Cursor prompts

v0 by Vercel (GPT-5.2 powered)

• Specialized for UI components
• Outputs shadcn/ui components
• One-click deploy to Vercel
• Explore v0 prompts

Google AI Studio (Gemini 3 Pro)

• Direct Gemini 3 access with 1M context
• Upload screenshots, get matching code
• "Generative interfaces" for interactive outputs
• Vertex AI for enterprise deployments

The Verdict: Gemini 3 Pro Just Makes Prettier UIs

Here's the honest truth that's hard to quantify: Gemini 3 Pro simply produces better-looking UIs. Not because of benchmarks or technical specs—it just does.

Give both models the same prompt—even a lazy, unoptimized one—and Gemini 3 Pro consistently outputs more visually pleasing results. The spacing feels better. The color choices are more harmonious. The overall "vibe" is more polished. We can't point to a specific metric, but developers who've used both know exactly what we mean.

Gemini 3 Pro Wins for UI/Design:

• It just looks better — subjective, but consistently true
• Works well even with minimal prompt optimization
• Better intuition for modern design trends
• More harmonious color palettes by default
• Superior spacing and visual hierarchy
• The "vibe-coding" hype is actually real

GPT-5.2 Wins for Everything Else:

• Complex business logic and backend integration
• Strict TypeScript and type safety
• Accessibility compliance (WCAG)
• Following exact specifications without "creative" deviations
• Better IDE integration (Cursor, v0)
• More predictable, consistent output

The Real Winner: Prompt Quality

Here's the truth both OpenAI and Google won't tell you: the quality of your prompts matters more than which AI you use. A well-crafted prompt in either GPT-5.2 or Gemini 3 Pro will outperform a lazy prompt in the "better" model every time.

The developers shipping the best UI code in 2025 are those who:

1. Use detailed, structured prompts with clear specifications
2. Include design system tokens and constraints upfront
3. Iterate with precise follow-up refinements
4. Match the right tool to the specific task
5. Leverage each model's unique strengths

Get Started with Battle-Tested Prompts

Skip the prompt engineering trial and error. Our curated prompt collection includes prompts optimized for both GPT-5.2 and Gemini 3:

• Landing page prompts
• Dashboard prompts
• SaaS UI prompts
• Cursor-optimized prompts
• v0-optimized prompts

The AI coding wars are hotter than ever. Whether you choose GPT-5.2, Gemini 3 Pro, or both—the developers who win are those who master how to communicate with these tools effectively.

Last updated: December 16, 2025