Claude vs GPT vs DeepSeek vs Gemini: Comparison of AI Models for Programming in 2025 — Which AI Writes Code Better?

## Introduction: The Battle of Neural Networks for Your Code The market for AI assistants for developers is overheated. Every month, a new model emerges promising a "revolution in coding." But when a real task arises—refactoring legacy code, hunting a bug at 3 AM, or generating a microservice from scratch—which AI truly won't let you down? We conducted a series of tests on real-world tasks to provide an objective **comparison of AI models**: Claude (Anthropic), GPT-4o (OpenAI), DeepSeek-Coder, and Gemini 2.0 (Google). We evaluated not only code quality but also generation speed, token cost, and the ability for multi-step reasoning. If you're looking for the perfect AI colleague for writing code, this article is your guide. ## 1. Task #1: Refactoring Spaghetti Code ### Participants: Claude 3.5 Sonnet vs GPT-4o vs DeepSeek-Coder V2 vs Gemini 2.0 Flash We gave each model the same Python block—150 lines with duplication, magic numbers, and no typing. **Results:** - **Claude 3.5 Sonnet** — suggested splitting the code into 4 classes, added type hints, and wrote docstrings. The only one that fixed a potential memory leak. **Quality: 10/10** - **GPT-4o** — reduced the code by 40% but left several implicit bugs (e.g., an unhandled exception). **Quality: 7/10** - **DeepSeek-Coder V2** — did a good refactoring but didn't remove commented-out junk. **Quality: 8/10** - **Gemini 2.0 Flash** — simply renamed variables. Essentially failed the task. **Quality: 4/10** **Conclusion:** For cleaning and organizing code, **Claude** is the best—it sees architecture, not just syntax. ## 2. Task #2: Debugging a Hidden Bug ### Test: Find a race condition in asynchronous code We designed a complex bug: a data race in asyncio with partially incorrect logical operators. Models had to not only find the error but also explain the cause. - **GPT-4o** — found the bug in 2 iterations, gave a correct explanation with a traceback. **Time: 45 sec** - **Claude 3.5** — found the bug instantly, but its explanation was too general. **Time: 30 sec** - **DeepSeek** — pointed to a wrong import (which didn't exist) but missed the actual bug. **Time: 60 sec** - **Gemini** — got stuck on one method and didn't see the problem. **Conclusion:** For debugging sessions where speed and accuracy are needed, **GPT-4o** remains the leader. Claude is good but can get lost in abstractions. ## 3. Task #3: Generating Code from Scratch ### Technical Specification: Write a REST API in FastAPI for a to-do list with authorization This was a test of understanding the full development cycle. Criteria: security (JWT), code cleanliness, documentation. - **Claude 3.5** — generated fully working code from scratch, including Alembic migrations and tests. The only one to use dependency injection correctly. **Winner** - **GPT-4o** — code worked but was redundant (200 lines vs. Claude's 150). - **DeepSeek** — produced a minimal working solution but without error handling. - **Gemini** — output code that didn't run due to a syntax error in Pydantic. **Conclusion:** If you need to write code from scratch for a complex architecture, choose **Claude**. For simple scripts, any will do, but Claude delivers production-ready solutions. ## 4. Price and Speed: What's More Profitable? We compared the cost of 1 million tokens (input/output) and the generation time for an average response (500 tokens): | Model | Input | Output | Speed (sec) | |--------|------|-------|----------------| | GPT-4o | $5 | $15 | 2.5 | | Claude 3.5 Sonnet | $3 | $15 | 3.0 | | DeepSeek-Coder V2 | $0.14 | $0.42 | 1.2 | | Gemini 2.0 Flash | $0.10 | $0.40 | 0.8 | **Analysis:** - **Gemini** — the cheapest and fastest, but code quality suffers. - **DeepSeek** — excellent balance of price and quality for routine tasks. Ideal for writing simple functions. - **Claude and GPT** — premium segment. Expensive but pay off on complex projects. ## 5. Verdict: Which Model to Choose? ### Final **comparison of AI models** by scenario: - **For refactoring legacy code**

Claude vs GPT vs DeepSeek vs Gemini: Comparison of AI Models for Programming in 2025 — Which AI Writes Code Better?

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