Claude 3.5 vs ChatGPT-4o: Side-by-Side Comparison for Real Tasks

Both Claude 3.5 Sonnet and ChatGPT-4o are excellent AI assistants. But “excellent” doesn’t tell you which one to use. When you’re paying for a subscription or building a workflow around an AI, you want specifics.

So we ran both through the same real-world tasks — writing, coding, research, summarization, and reasoning — and tracked where each one actually shines.

Here’s what we found.

The Basics

Claude 3.5 Sonnet is Anthropic’s flagship model as of late 2025. It’s available through Claude.ai (free tier included) and via API. It’s known for long-context handling, nuanced writing, and strong instruction-following.

ChatGPT-4o is OpenAI’s current default model in ChatGPT. It’s multimodal (text, image, voice), deeply integrated with tools like DALL·E, Code Interpreter, and web browsing. The free tier has access, but Plus ($20/month) unlocks full usage.

Both are capable. But they have different personalities, strengths, and failure modes.

Task 1: Long-Form Writing

Prompt: “Write a 600-word blog post about the benefits of walking for mental health. Make it feel personal and conversational, not clinical.”

Claude 3.5 delivered a post that felt genuinely human. It opened with a scene — a specific moment on a trail — rather than a generic intro. The tone stayed consistent throughout, and it avoided the tendency to over-list things.

ChatGPT-4o produced clean, well-structured content with good information density. It was more polished in a textbook sense, but also more generic. The opening was a thesis statement rather than a hook.

Winner: Claude 3.5 — for tone control and avoiding “AI voice,” it’s noticeably better.

Task 2: Coding

Prompt: “Write a Python script that reads a CSV file, filters rows where the ‘status’ column is ‘active’, and outputs a new CSV.”

Both models produced working code. No surprises there.

Claude 3.5 added error handling for missing files and explained each section with inline comments. The code was clean and immediately usable.

ChatGPT-4o also produced working code and offered to extend it — adding command-line arguments, for example. It’s slightly more likely to anticipate follow-up needs.

Winner: Tie — both nail basic coding tasks. ChatGPT-4o has an edge if you want it to iteratively build on code; Claude has an edge on code clarity.

Task 3: Document Summarization

Prompt: We fed both a 15-page research paper and asked for a 200-word summary highlighting key findings.

Claude 3.5 handled this exceptionally well. Its 200k context window means it can process long documents without chunking. The summary was accurate, prioritized the right findings, and didn’t hallucinate methodology details.

ChatGPT-4o performed well but occasionally abstracted too aggressively — losing specific numbers and nuances that were in the original. Without file upload, you’re limited to pasting text, which hits token limits faster.

Winner: Claude 3.5 — better long-document handling, fewer hallucinations on specific details.

Task 4: Reasoning and Logic

Prompt: A classic multi-step logic puzzle involving scheduling constraints across five people.

Both models got the answer right. But Claude’s reasoning was more systematic — it laid out its working step by step in a way that made errors easy to spot. GPT-4o jumped to conclusions faster (sometimes correctly, sometimes not).

Winner: Claude 3.5 — for complex reasoning where you want to see the work.

Task 5: Web Research and Real-Time Info

This is where ChatGPT-4o wins decisively. It has built-in web browsing — it can pull current prices, recent news, live stock data, or anything published recently. Claude does not browse the web in the standard interface.

If your task requires up-to-date information, GPT-4o is the tool.

Winner: ChatGPT-4o — no contest when you need current data.

Task 6: Image Understanding

Both models accept image inputs. We uploaded a screenshot of a cluttered spreadsheet and asked for analysis.

ChatGPT-4o is deeply integrated with vision — it reads images faster, interprets charts well, and can combine image analysis with code execution (via Code Interpreter).

Claude 3.5 also handles images well but is less tightly integrated with downstream tools.

Winner: ChatGPT-4o — better multimodal pipeline, especially for images + code.

Pricing Comparison

Which One Should You Use?

Use Claude 3.5 if you:

• Write a lot (blogs, emails, reports, scripts)
• Need to summarize or analyze long documents
• Want more predictable, consistent output
• Do complex reasoning tasks

Use ChatGPT-4o if you:

• Need real-time web information
• Work with images + code together
• Want voice mode or DALL·E integration
• Rely on the GPT plugin/tool ecosystem

The Honest Take

Neither model is universally better. They’re different tools for overlapping jobs.

If I had to pick one for general knowledge work — writing, research, analysis — I’d lean Claude 3.5. If I needed a Swiss Army knife with web access and multimodal tools, I’d reach for ChatGPT-4o.

Most serious users end up with both. That’s not a cop-out — it’s just accurate. At $20/month each, having both gives you coverage for nearly any task you’ll encounter.

Try the free tiers of both before committing. Your use case will tell you which one fits.