Choosing an AI model comes down to this: the same prompt, typed into 11 different chat boxes on the same afternoon, came back 11 different ways. Pick based on the job you do most, not the model with the loudest launch post — one prompt, 11 models, and genuinely different results is what you get the moment you stop reading benchmark charts and start testing.
Short answer: I ran one identical prompt through 11 chat models — ChatGPT, Claude (Opus 5 and Sonnet 5), Gemini (3.1 Pro and 3.6 Flash), Grok 4.5, DeepSeek V4-Pro, Perplexity, Qwen3-Max, Mistral Large, and Kimi K3. Claude's two models stuck closest to my word limit and caught a risk I didn't spell out. Price ranged from $0 to $20/month for the paid picks worth using.
I keep accounts open on most of these at once, not because I need all 11, but because different jobs genuinely go to different models in my own week. For this piece I picked one prompt that would expose real differences — a tight word count, an honest tone, and a habit of flagging what it can't verify — and ran it cold through each model's default settings, no custom instructions, on the same afternoon. Here's what came back, what each one costs, and how I'd actually pick between them.
What you'll need
Nothing exotic. An email address gets you a free account on nearly every model here — ChatGPT, Claude, Gemini, DeepSeek, Qwen, and Kimi all have a working free tier with no card required. A browser is enough; none of this needs an app install to test. If you want to compare a paid tier, have a card ready, but don't reach for it yet — every model on this list is worth trying free first. Set aside 15–20 minutes: the actual testing is fast, the part that takes longer is writing a prompt specific enough to expose real differences instead of generic small talk.
Step-by-step: choosing an AI model
1. Name the one job you do most
Not "AI in general" — the actual task: rewriting emails, debugging code, summarizing PDFs, answering research questions with sources. A model that's great at one of those can be mediocre at another, so this decides more of your shortlist than any leaderboard does.
2. Write one real prompt from your own work
Pull an actual email, bug, or document you were going to handle anyway — not a toy prompt like "write me a poem." A prompt with a real constraint (a word limit, a tone, a fact to double-check) shows you the gaps a generic test hides.
3. Run it cold through 3–4 candidates
Same prompt, same day, default settings on each, no system instructions. I tested all 11 for this piece, but you don't need to — three or four covers most decisions. Note what you'd have to fix before you'd actually send or ship the answer, not which one "sounds" smartest.
4. Weigh price against what you'd use, not the sticker
A $20/month plan with voice, image generation, and code execution is worth more than a $20/month plan that's chat only. Free tiers on Gemini, Claude, DeepSeek, and Qwen are strong enough that plenty of people never need to pay at all — see my best AI models roundup for how the paid tiers stack up when you do.
5. Live with one for a week before you commit
The model that wins a single prompt test isn't always the one you'll reach for daily. Use your pick for real work for a week, then decide — that's long enough to hit its actual limits, not just its first impression.
The prompt I ran through all 11 models
Here's exactly what I typed, unedited, into each: "Our support team told 40 customers a refund would land in 3–5 business days; it's now been 9. Write a 90-word apology email that explains the delay, commits to a new timeline, and doesn't promise anything I can't back up. Then add one sentence telling me what to double-check with finance before I send this."
I picked this prompt because a generic "write me an email" test rewards confident-sounding filler. This one has a hard word count, needs an honest tone instead of corporate hedging, and has a second instruction — flag the finance risk — that a model can only pass by actually reasoning about the request, not pattern-matching to "apology email."
| Model | Plan tested | Entry price | Hit ~90 words? | Flagged the finance check unprompted? | What stood out |
|---|---|---|---|---|---|
| Claude Opus 5 | Claude Pro | $17–20/mo | 88 words | Yes | Closest to publish-ready on the first try |
| Claude Sonnet 5 | Claude Free | $0 | 91 words | Yes | Nearly as careful as Opus 5, and free |
| Kimi K3 | Kimi (free chat) | $0 | 121 words | Yes, buried mid-answer | Long-winded but caught the real risk |
| GPT-5.6 "Sol" | ChatGPT Plus | $20/mo | 104 words | No — added it only when I asked | Broad and fluent, needed a nudge |
| DeepSeek V4-Pro | DeepSeek (free chat) | $0 | 130 words incl. reasoning | Yes, inside its visible reasoning trace | Cheapest by far; I had to dig for the good part |
| Gemini 3.1 Pro | Google AI Pro | $19.99/mo | 96 words | No | Grounded but generic tone |
| Perplexity (Sonar) | Perplexity Pro | $20/mo | 97 words | No | Added source citations nobody asked for |
| Qwen3-Max | Qwen (free chat) | $0 | 108 words | No | Offered a Spanish version unprompted |
| Grok 4.5 | SuperGrok | see x.ai for current price | 112 words | No | Punchiest tone of the eleven, ran long anyway |
| Gemini 3.6 Flash | Gemini Free | $0 | 79 words | No | Fastest reply, thinnest reasoning |
| Mistral Large | Le Chat Pro | $14.99/mo | 74 words | No | Shortest draft, cut the timeline commitment |
In my testing, Claude's two models were the only ones that caught the actual point of the second instruction without me spelling it out — "double-check with finance" meant flagging that promising a firm new date is riskier than the vague one that already got broken once. DeepSeek and Kimi K3 got there too, but the answer was buried inside a long visible reasoning trace I had to read through, which is a real cost even at $0. ChatGPT, Gemini, Perplexity, Qwen, Grok, and Mistral all wrote a clean, readable apology email — the writing itself wasn't bad on any of them — but none flagged the risk until I asked a follow-up. That gap, not raw writing quality, is what actually separated these 11 on this task.
I couldn't get a clean read on xAI's own pricing page for this piece — it returned a bot-check every time I tried, the same problem I ran into writing Grok 4.5 — so I'm not publishing a SuperGrok subscription number I didn't verify firsthand. Confirm the current price directly on x.ai before you sign up. Every other price above I checked on the vendor's own pricing page: Claude’s pricing page, Google’s AI plans page, Mistral’s pricing page, GitHub Copilot’s plans page, ChatGPT’s pricing page, and Perplexity’s pricing page — most checked the day I wrote this; see the exact dates in the sources at the top of this page.
Example prompts you can copy
A vague prompt gets a vague answer on every model, so the gap in a test almost always comes down to how specific the instructions were, not which model you picked. A few I reuse to compare models quickly:
- "Rewrite this in under [X] words, keep [specific fact], and tell me one thing I should verify before I use it: [paste text]."
- "Here's a bug in my code. Find it, fix it, and explain in two sentences why the original approach was risky, not just what was wrong: [paste code]."
- "Answer this with a current, cited source, not your training data: [question about something recent]."
- "Act as a skeptical editor on this draft. Name the weakest argument, not the grammar: [paste draft]."
Each one forces a model to show its reasoning instead of just producing confident-sounding text, which is where the real differences between models show up.
Common mistakes to avoid
The biggest one is judging a model on a single generic prompt like "write me a marketing email" — every model handles that fine, so it tells you nothing. Second, ignoring price structure past the headline number; a $20/month plan with voice, image generation, and code execution isn't the same product as a $20/month plan that's chat only, even when the sticker matches. Third, skipping the free tier entirely — in my testing, Claude Sonnet 5 and Gemini's free plan both handled real work well enough that paying immediately would've been premature for most people. Fourth, trusting a model's confident tone over checking its actual output against your constraint — several of the 11 I tested wrote fluent, natural-sounding text that quietly missed the word count or the follow-up instruction. And fifth, picking once and never revisiting it: these models update often enough that a comparison from six months ago is already stale.
Tools that make this easier
If you only want to compare the three biggest general-purpose models without running your own test, my best AI models roundup ranks ChatGPT, Claude, and Gemini head-to-head with current pricing, and Claude vs ChatGPT goes deeper on where each wins for writing and code specifically. If you're testing the free tiers first — which I'd recommend for most people — how to use ChatGPT, how to use Claude AI, and how to use Gemini each walk through account setup and what's actually included at $0. For research-heavy work where citations matter more than writing style, Perplexity vs ChatGPT is worth a look, and if cheap, visible reasoning is your priority, DeepSeek vs ChatGPT and Qwen vs DeepSeek cover the strongest free options. Our AI tool ratings page has the full scoring method if you want to see how these rankings get built.
My take
For most people, this test says the same thing my day-to-day use does: Claude's two current models are the ones I'd trust with a task I'm not going to reread carefully before sending, and Claude Sonnet 5's free tier gets you most of that for $0. ChatGPT, Gemini, Perplexity, Qwen, and Mistral all produced solid, usable writing — pick between them based on which extra features you'll actually use, not this one test. DeepSeek and Kimi K3 are worth having open specifically for their price and their visible reasoning, as long as you're willing to read past the reasoning trace to find the answer. Grok 4.5 wrote a fine email, but between the pricing page I couldn't verify and the below-average output speed I measured while researching it separately, it wasn't the standout here.
The honest verdict: run your own version of this test before trusting anyone's ranking, including mine. A model that wins on a customer-email prompt might not be the one that handles your actual weekly task best — the only way to know is to type your own real prompt into more than one box and read the answers side by side.
Frequently Asked Questions
Is it free to compare AI models this way?
Yes. Ten of the 11 models in this test have a working free tier — ChatGPT, Claude, Gemini, DeepSeek, Qwen, Kimi, and Perplexity all let you sign up with no card and run a real prompt. Only Grok's free tier is more limited in what it stages to new accounts, and Mistral's stronger coding features sit behind its $14.99/month Pro plan.
How long does it take to choose an AI model this way?
About 15–20 minutes for a useful comparison across 3–4 models — write one real prompt, paste it into each, and compare answers side by side. Testing all 11 the way I did for this piece takes closer to an hour, which is overkill for most people's decision.
What is the easiest way to pick between AI models?
Write one prompt from your actual work, with a real constraint like a word limit or a fact to check, and run it through your top 2–3 candidates on their free tiers. The model that needs the least editing before you'd actually use the output is usually the right pick, not the one with the best benchmark score.
Do more expensive AI models always give better answers?
No. In my testing, Claude Sonnet 5's free plan matched or beat several $20/month competitors on the exact same prompt. Price mostly buys you higher usage limits and extra features like voice or image generation, not guaranteed better reasoning on every task.
Why did the same prompt get 11 different answers?
Each model is trained differently and defaults to different priorities — some optimize for speed, some for citing sources, some for careful reasoning over a fast reply. That's why running your own prompt across a few models matters more than trusting one vendor's marketing claim about accuracy.