Model comparisons - tested October 2026 by Vitus Pruser. How we test.
Verdict
GPT-6 Astra took 7 of 10 prompts in the blind ranking, mostly on precision: exact UN population figures, fuller data tables and tighter reasoning answers. Gemini 3.1 Pro Preview won the writing brief (the only answer that hit 120 words with a subject line) and produced the only cent-rounding fix that is correct on the boundary cases. Both finished every task with zero hallucinations. Pick GPT-6 Astra for direct, precise answers; Gemini when you want the working shown or code reviewed.
Verdict by task
| Task | Winner | Why |
|---|
| Writing | Gemini 3.1 Pro Preview | Hit the 120 word email target exactly and included a subject line; its rewrite also glossed exponential and linear for a young reader. GPT-6 Astra was close but skipped the subject. |
| Coding | Split | Both passed all of their own tests on slugify. GPT-6 Astra wrote the leaner implementation; Gemini produced the only cent-rounding fix that stays correct on the boundary cases. |
| Research | GPT-6 Astra | Both were accurate on the EU VAT scheme; GPT-6 Astra also flagged honestly that it cannot verify later amendments, and its population figures matched the UN 2024 estimates exactly. |
| Data analysis | GPT-6 Astra | Both got every number right. GPT-6 Astra ranked first for richer tables and the more rigorous MRR rounding; Gemini showed the clearest working. |
| Reasoning | GPT-6 Astra | Both solved both puzzles in the optimal 6 steps and the correct 41/73/73 split; GPT-6 Astra presented jug states and the check more compactly. |
Results, prompt by prompt
writing - winner: Gemini 3.1 Pro Preview
Prompt: Write a 120 word product update email to existing customers of a small accounting software company announcing that bank feeds now sync every hour instead of once a day. Plain, friendly, no exclamation marks, end with one clear call to action.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 34.7s. Exactly 120 words with a subject line: the only answer to hit the brief precisely.
- GPT-6 Astra - pass, no hallucinations, 16.1s. 124 words, plain and friendly, ends with a clear log in call to action. No subject line.
writing - winner: Gemini 3.1 Pro Preview
Prompt: Rewrite this paragraph so a 12 year old understands it, keep every fact, max 80 words: 'Compound interest is interest calculated on the initial principal and also on the accumulated interest of previous periods. Because the base grows each period, the growth is exponential rather than linear, which is why long time horizons matter far more than the interest rate alone.'
- Gemini 3.1 Pro Preview - pass, no hallucinations, 13.7s. 65 words, keeps all facts and glosses exponential and linear in brackets for a young reader.
- GPT-6 Astra - pass, no hallucinations, 12.5s. 66 words, keeps every fact including exponential versus linear growth. Cleanest rewrite.
coding - winner: GPT-6 Astra
Prompt: Write a Python function slugify(title: str) -> str that lowercases, replaces any run of non alphanumeric characters with a single hyphen, strips leading and trailing hyphens, and transliterates common accented Latin letters (e, a, o, u with accents, and the German sharp s) to ASCII. Include 5 pytest test cases. No external dependencies.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 27.4s. All 5 tests pass. Thorough docs plus how to run the suite.
- GPT-6 Astra - pass, no hallucinations, 22.6s. Leanest correct solution: casefold() handles ß naturally. All 5 tests pass and it survives extra edge cases (Ü, Ñ).
coding - winner: Gemini 3.1 Pro Preview
Prompt: This JavaScript has a bug: users report the total is sometimes off by one cent. Find the bug, explain it in two sentences, and give the corrected function.
function total(items) {
let sum = 0;
for (const it of items) {
sum += it.price * it.qty * (1 + it.taxRate);
}
return Math.round(sum * 100) / 100;
}
- Gemini 3.1 Pro Preview - pass, no hallucinations, 100.3s. The only fix that stays correct on the boundary cases: exponential-notation scaling keeps the original rounding policy. Needed 100s of thinking.
- GPT-6 Astra - pass, no hallucinations, 17s. Correct diagnosis and a Decimal.js fix that is exact on every boundary case, but it adds an npm dependency.
research - winner: GPT-6 Astra
Prompt: What is the current EU VAT registration threshold for small businesses under the EU wide SME scheme that started in 2025, in euros, and which regulation introduced it? Answer in 3 sentences and say if you are unsure about any figure.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 14.5s. Correct figures and instrument, stated confidently. Less nuance than Claude on national thresholds.
- GPT-6 Astra - pass, no hallucinations, 13.4s. Correct figures (€100,000 union threshold, €85,000 national cap), correct instrument (Directive 2020/285), and honestly flags it cannot verify later amendments.
research - winner: GPT-6 Astra
Prompt: List the 5 largest countries by population in 2024 with their approximate population, and name the source you would cite for these figures. Table format.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 11s. Correct ranking and the right source named, but figures run about 2 to 6m below UN 2024 estimates.
- GPT-6 Astra - pass, no hallucinations, 11s. Most precise figures (India 1.451b, China 1.419b), matching UN World Population Prospects 2024 mid-year estimates, with the source named.
data - winner: GPT-6 Astra
Prompt: Here are monthly revenue figures in EUR for a shop: Jan 41200, Feb 38900, Mar 45100, Apr 47800, May 46200, Jun 52300, Jul 55900, Aug 51400, Sep 58700. Compute the month over month growth for each month, the average growth rate, and the best and worst month. Show the numbers in a table and state the totals.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 18.2s. All figures correct with a clean layout and the formula stated.
- GPT-6 Astra - pass, no hallucinations, 20.6s. Every month over month figure correct (avg 4.90%), plus euro changes, totals and a multi-metric best and worst table.
data - winner: GPT-6 Astra
Prompt: A SaaS company has 1,240 customers paying an average of 49 EUR per month and loses 3.1 percent of customers each month. New signups are 85 per month. Estimate the customer count and MRR after 12 months assuming these rates hold. Show your working and round to whole numbers.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 27.8s. 1,713 and 83,937 with the clearest step-by-step working of the five.
- GPT-6 Astra - pass, no hallucinations, 23s. Closed-form solution, 1,713 customers, MRR 83,920 computed on the unrounded count, which is the more rigorous route.
reasoning - winner: GPT-6 Astra
Prompt: I have a 3 litre jug and a 5 litre jug and unlimited water. Give the shortest sequence of steps to measure exactly 4 litres. Then say how many steps it took.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 13.4s. Optimal 6 steps with the clearest narration of jug states.
- GPT-6 Astra - pass, no hallucinations, 11.1s. Optimal 6 steps with per-step jug states shown.
reasoning - winner: GPT-6 Astra
Prompt: Three colleagues need to split a 187 EUR dinner. Anna had no drinks and her food was 41 EUR. Ben and Clara shared two bottles of wine totalling 58 EUR and their food was 44 EUR each. Who owes what, so that everyone pays exactly for what they consumed? Show the check that the parts add up to 187.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 8.6s. 41, 73, 73, correct with explicit per-person lines.
- GPT-6 Astra - pass, no hallucinations, 8.6s. 41, 73, 73, check to 187. Correct and cleanest.
Frequently asked questions
Is Gemini or ChatGPT better?
In our October 2026 round, GPT-6 Astra ranked first on 7 of 10 prompts in a blind review. Gemini 3.1 Pro Preview won the product email, the plain-English rewrite and the rounding bug fix. Both passed every task with zero hallucinations: the difference is style, with Gemini explaining more and GPT-6 Astra sticking closer to the brief.
Is Gemini or ChatGPT better for coding?
Both wrote slugify implementations that passed all five of their own tests. GPT-6 Astra produced the leaner code, but Gemini 3.1 Pro Preview gave the only cent-rounding fix that stays correct on the classic 1.005 boundary case, so for code review Gemini has a real edge.
Which is cheaper, Gemini or ChatGPT?
Measured in Krater across the ten prompts, GPT-6 Astra cost $0.21 in total and Gemini 3.1 Pro Preview $0.39, with most of Gemini's gap coming from 100 seconds of extended thinking on the hardest coding task. On everyday prompts the two are close.
Can I use Gemini and ChatGPT in the same place?
Yes. Krater gives you Gemini 3.1 Pro Preview, GPT-6 Astra and 500+ other models in one workspace, and the Model Arena lets you send one prompt to several models side by side, which is exactly how this comparison was run.
How was this comparison tested?
All five models (GPT-6 Astra, Claude Fable 5.1, Gemini 3.1 Pro Preview, Grok 4.3 and Perplexity Sonar Pro) received the same ten prompts side by side in the Krater Model Arena on 7 October 2026, with default settings and no system prompt; this page compares the two you are looking at. We recorded time to a complete answer and the real model cost per answer, ran the generated code through its own test suites, fact checked every claim, scored completion as pass, partial or fail, and then ranked the answers blind. The full procedure is on our methodology page.
Will this comparison be updated?
Yes. Flagship comparisons are rerun monthly and whenever a provider ships a new version. The tested month and model versions are shown at the top of the page.
