The short answer
To compare AI answers, paste one unchanged prompt into fresh chats in two or three assistants, such as ChatGPT, Claude and Gemini, note which model each used, then mark where the answers disagree and check those claims first. Perplexity's Model Council automates this on the Max plan: it runs three models and shows where they agree and differ. Anthropic lists comparing repeated answers as a way to spot hallucinations, because inconsistent claims are often the wrong ones.
Why compare AI answers at all
Asking two AI models the same question is the cheapest quality check there is. When ChatGPT, Claude and Gemini agree and cite the same sources, you can move faster. When they disagree, you have found exactly the claim that needs checking. Anthropic even lists this as a technique in its guide to reducing hallucinations: run the same prompt several times and compare the outputs, because inconsistencies can point to made-up information.
Comparing also tells you which tool suits a kind of work. The model that writes your emails best may not be the one that analyses your spreadsheet best, and the only reliable way to find out is to test your own tasks, not someone else's benchmark.
What you need first
- Two or three assistants open in separate tabs. Free plans are enough to start: ChatGPT, Claude and Gemini all have one.
- One fixed prompt, written once and pasted unchanged into each tool. See how to write a good prompt.
- The same material for each tool, if the task uses a file.
- A short scorecard: three or four things you care about, such as accuracy, usefulness, tone and time saved.
How to compare AI answers in 7 steps
- Pick a real task you do every week. A client email, a meeting summary, a market question. Real tasks show real differences.
- Write the prompt once and freeze it. Any change in wording between tools makes the comparison meaningless.
- Match the settings as closely as you can. Note the model and mode each tool used: ChatGPT answers with GPT-6 Sol on Plus, Pro, Business and Enterprise, Claude offers Claude Opus 5.5 from the Pro plan and Gemini 4 Argon needs Google AI Pro or Ultra, while smaller plans use smaller models (GPT-6 Luna on ChatGPT Free and Go; Claude Sonnet and Haiku on Claude Free; mostly Flash-Lite on free Gemini and Flash on Google AI Plus). A free model against a paid one is not a fair test.
- Paste the prompt into fresh chats. Memory and earlier messages change answers, so start clean in each tool.
- Read the answers side by side and mark disagreements. Where they differ on a fact, that fact goes on your checking list.
- Score each answer against your scorecard before you decide which you like. Fluency is persuasive, so score accuracy first.
- Repeat with two more tasks before you decide on a tool for that kind of work. One prompt is an anecdote; three is a pattern.
How to compare AI answers automatically with Perplexity Model Council
Perplexity has a feature that does the side-by-side work for you. Model Council runs your question across three models (by default one frontier model each from Anthropic, OpenAI and Google), then a synthesiser model writes one combined answer that shows where they agree, where they differ and any finding only one model surfaced. The contributing models are named under the answer.
- Go to the Perplexity homepage on the web.
- Click Search below the search bar and select Model Council.
- To change the line-up, click 3 models and switch models on or off. Each has a Thinking toggle for deeper reasoning.
- Type your question and press Enter.
The catch is the plan. In Search, Model Council is included with Perplexity Max and Enterprise Max, not with Free or Pro, and it has a monthly query cap. It is also on iOS from app version 26.16.0, but not yet a search mode in the Android or desktop apps. In Perplexity Computer, any paid plan can run a council of two to eight models, which uses Computer credits. See how to use Perplexity for the plans.
A worked example: three answers to one pricing question
A marketing lead wants to know which of three competitors offers a free plan and what it includes. She writes one prompt: "For [competitor A], [competitor B] and [competitor C], tell me whether each has a free plan as of this month, what it includes and its main limit. Link the official pricing page for each and say 'not found' if you cannot confirm something."
- Two assistants agree on A and C and link the same official pricing pages.
- On B, one says there is a free plan, another says it was replaced by a trial, and the third gives no link.
- She opens B's pricing page herself. The trial answer is right; the other answer was based on an old page.
The comparison took four minutes and pointed straight to the one claim that would have embarrassed her in the meeting. It also showed which assistant links its sources by default, which is useful to know next time.
Common mistakes when comparing AI answers and how to fix them
- Changing the prompt between tools. Fix: copy the exact same text every time.
- Comparing a free model with a paid one. Fix: note the model used, and compare like with like.
- Judging on style. The longer, more confident answer often wins on first read. Fix: score accuracy before tone.
- Treating agreement as proof. Models trained on similar data can repeat the same error. Fix: still open the sources for the claims that matter.
- Testing on trivia instead of your work. Fix: use the tasks you actually do.
- Pasting sensitive data into every tool. Fix: check each tool's training setting first. Personal ChatGPT, Claude and Perplexity accounts can train on chats unless you opt out.
Which tools to use for comparing answers
- Manual side by side in ChatGPT, Claude and Gemini: free, flexible and the best way to choose a tool for your own work.
- Perplexity Model Council: the fastest automatic comparison if you are on Max, with agreement and disagreement shown for you.
- Yuzoki's compare page: sets tools side by side for common tasks, and our head-to-head guides such as ChatGPT vs Claude, ChatGPT vs Gemini and Claude vs Gemini give a verdict for each kind of work.
For a disagreement you need to settle, follow how to check if AI is telling the truth.
4 prompts for comparing AI answers
Prompts to copy
A comparison-ready prompt
[Your task]. Use this structure: a two-sentence answer, then the reasoning in up to five bullet points, then a list of every factual claim with a source link or "no source". If you are unsure about anything, say so.
You get: Answers from different tools in the same shape, easy to compare
Reconcile two answers
Below are two AI answers to the same question: "[question]". List where they agree, where they disagree and anything only one of them mentions. For each disagreement, say what evidence would settle it and, if you can search, find it. Answer A: [paste] Answer B: [paste]
You get: A clear list of agreements, conflicts and how to resolve them
Score answers against your criteria
Score each of these answers from 1 to 5 on accuracy, usefulness for [reader], clarity and tone. Justify each score in one sentence and say which answer you would send and what you would change in it. [paste answers]
You get: A scored comparison with a recommendation
Run it again for consistency
Answer this question three separate times, as if each were a fresh attempt, without referring to your other attempts: [question]. Then compare your three answers and list any facts that changed between them.
You get: A quick consistency check that exposes shaky claims