Choosing the right AI model isn't just about which is "smartest" — it's about which one handles your specific task best. This compares the current default tier of each: ChatGPT running on GPT-6, Claude, and Gemini 3.8 Flash.
TL;DR — Which to use when
| Task | Best model |
|---|---|
| Writing & editing | Claude |
| Coding & debugging | ChatGPT or Claude |
| Long document analysis | Either (both ~1M context now) |
| Real-time web info | Gemini or ChatGPT (with search) |
| Video understanding | Gemini (the only one that takes video directly) |
| Following complex instructions | Claude |
| Data analysis with Python | ChatGPT (code execution) |
| Guaranteed schema-valid JSON | ChatGPT |
ChatGPT (GPT-6)
Made by: OpenAI
Strengths
- Code execution: upload files, run Python, generate charts.
- Structured outputs: strict, schema-validated JSON via the Responses API.
- Tool ecosystem: the largest third-party plugin and integration ecosystem.
- Reasoning tiers: GPT-6 Astra, Sol and Luna give you a capability/cost dial without changing products.
Weaknesses
- Can be verbose — tends to hedge and add caveats even when not needed.
- Doesn't take video or audio directly in chat (Gemini does).
Best prompt style
GPT-6 responds well to clear, direct Markdown-formatted prompts. Use headers and bullet points to structure complex instructions, and skip "think step by step" — it reasons internally now.
You are a senior data analyst. Given the CSV below, analyze sales trends
by region and output a brief summary table followed by 3 key insights.
[CSV data here]
Claude (Fable 5.1 / Opus 5.5 / Sonnet 5)
Made by: Anthropic
Strengths
- Instruction-following: exceptionally good at following complex, multi-part instructions precisely.
- Long document analysis: current models take up to a 1M-token context window.
- Writing quality: natural, nuanced prose.
- XML tags: responds especially well to XML-structured prompts.
- Adaptive thinking: reasons internally before answering, with an effort dial for depth.
Weaknesses
- No built-in code execution in the standard chat product the way ChatGPT has.
- Sometimes overly cautious on edge-case requests.
Best prompt style
Claude shines with XML-structured prompts and explicit formatting instructions.
You are an expert technical writer.
<document>
[paste document here]
</document>
<task>
Summarize this document into:
1. A 2-sentence executive summary
2. 5 key bullet points
3. One recommended action
</task>
Output only the structured summary — no preamble.
Gemini (3.8 Flash)
Made by: Google
Strengths
- Multimodal: the only one of the three that takes video and audio directly, alongside images, PDFs and text.
- Google Search grounding: real-time web access with citations, built in.
- Speed and price: fast, and cheap relative to flagship tiers of the other two.
- Google Workspace integration: a natural fit if you live in Docs, Sheets, Gmail.
Weaknesses
- Writing quality is often slightly behind Claude for nuanced prose.
- Output limit (65,536 tokens) is lower than GPT-6 or Claude's 128K, which matters for very long generated documents.
Best prompt style
Gemini works well with clear, direct instructions and is the strongest of the three at multimodal tasks — especially video.
Look at this chart [attach image].
Tell me:
1. What trend is shown over time?
2. What's the highest data point and when did it occur?
3. What's a possible explanation for the dip in Q3?
Which one should you start with?
If you're a beginner: start with whichever product you already have an account for — the fundamentals (clarity, context, format, examples) transfer across all three, and most tutorials work with any of them.
If you write or work with long documents: use Claude. The instruction-following and writing quality are strong, and the context window is no longer a differentiator on its own.
If your input is video, audio or you need real-time search: Gemini is your best bet — it's the only one that takes video directly.
If you need guaranteed schema-valid JSON or heavy tool use: ChatGPT on GPT-6 has the most mature structured-output guarantees.
If you're building a product: test all three on your real prompts and measure. Our Promptfoo tutorial sets this up in one config file. Never assume — always measure.
The model-agnostic truth
The quality of your prompt matters more than which model you pick. A great prompt on ChatGPT will beat a bad prompt on Claude every time.
Master the fundamentals — clarity, context, format, examples — and you'll get excellent results from any of these models. Current specs and prices for all three are on the models page, and the full breakdown by task is in GPT-6 vs Claude vs Gemini.
