Model comparisons - tested October 2026 by Vitus Pruser. How we test.
Verdict
Claude Fable 5.1 took 8 of 10 prompts on depth: the best-documented code, the most complete research answers and the only data answers that added context like the steady-state ceiling and compound growth. Gemini 3.1 Pro Preview hit the 120-word email brief exactly and produced the only cent-rounding fix that is still correct on the boundary cases. Claude thought the longest and cost the most in the round; Gemini was middling on both. Pick Claude when the analysis matters; pick Gemini when you want the brief followed exactly.
Verdict by task
| Task | Winner | Why |
|---|
| Writing | Split | Gemini hit the 120-word email target exactly with a subject line; Claude ran 9% over but wrote the friendlier rewrite with a snowball image a 12 year old gets. |
| Coding | Split | Both passed every slugify test. Claude documented its approach best; Gemini produced the only rounding fix that survives the 1.005 boundary case, so each won one task. |
| Research | Claude Fable 5.1 | Claude named both the directive and the accompanying regulation on EU VAT and gave cleaner UN population figures; Gemini was correct but lighter on nuance. |
| Data analysis | Claude Fable 5.1 | Both got every number right; Claude added average revenue, compound monthly growth, the month-by-month table and the steady-state ceiling. |
| Reasoning | Claude Fable 5.1 | Both solved both puzzles optimally; Claude proved the jug route is minimal and double-checked the bill split. |
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.
- Claude Fable 5.1 - pass, no hallucinations, 33.5s. 131 words, about 9% over target, but the most complete email: subject line, signoff and a support line. Best copy.
- 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.
writing - winner: Claude Fable 5.1
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.'
- Claude Fable 5.1 - pass, no hallucinations, 11.3s. 74 words, snowball image, keeps every fact. Friendliest read for a 12 year old.
- 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.
coding - winner: Claude Fable 5.1
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.
- Claude Fable 5.1 - pass, no hallucinations, 19s. All 5 tests pass. Best documented approach, with an explicit map for ß, æ, ø and a note on why.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 27.4s. All 5 tests pass. Thorough docs plus how to run the suite.
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;
}
- Claude Fable 5.1 - pass, no hallucinations, 99.1s. Correct diagnosis plus a working integer-cents fix, and it explicitly documents the per-line rounding trade-off. Slowest at 99s.
- 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.
research - winner: Claude Fable 5.1
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.
- Claude Fable 5.1 - pass, no hallucinations, 12.2s. Correct figures, names the accompanying Regulation 2020/283, and notes national thresholds vary. Most complete.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 14.5s. Correct figures and instrument, stated confidently. Less nuance than Claude on national thresholds.
research - winner: Claude Fable 5.1
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.
- Claude Fable 5.1 - pass, no hallucinations, 11s. Correct UN figures (~1.45b India) and the best source guidance: UN WPP plus named alternatives.
- 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.
data - winner: Claude Fable 5.1
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.
- Claude Fable 5.1 - pass, no hallucinations, 22.1s. All figures correct plus average revenue, compound monthly growth and the sawtooth trend call. Thorough.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 18.2s. All figures correct with a clean layout and the formula stated.
data - winner: Claude Fable 5.1
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.
- Claude Fable 5.1 - pass, no hallucinations, 25.3s. 1,713 customers and 83,937 EUR, plus a month-by-month table and the 2,742 steady-state ceiling insight.
- 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.
reasoning - winner: Claude Fable 5.1
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.
- Claude Fable 5.1 - pass, no hallucinations, 13.4s. Optimal 6 steps and proves it: the alternative route needs 8.
- Gemini 3.1 Pro Preview - pass, no hallucinations, 13.4s. Optimal 6 steps with the clearest narration of jug states.
reasoning - winner: Claude Fable 5.1
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.
- Claude Fable 5.1 - pass, no hallucinations, 8.6s. 41, 73, 73, plus a second verification (food 129 + wine 58).
- Gemini 3.1 Pro Preview - pass, no hallucinations, 8.6s. 41, 73, 73, correct with explicit per-person lines.
Frequently asked questions
Is Claude or Gemini better?
In our October 2026 round, Claude Fable 5.1 ranked first on 8 of 10 prompts in a blind review on the strength of deeper, better-documented answers. Gemini 3.1 Pro Preview won the brief-tight email and the rounding fix. Both finished every task with zero hallucinations.
Is Claude or Gemini better for coding?
Split. Claude wrote the best-documented slugify and passed everything; Gemini produced the only cent-rounding fix that stays correct on boundary cases. Claude explains its code better; Gemini's fixes are more literally correct.
Which is cheaper, Claude or Gemini?
Almost identical: $0.42 for Claude Fable 5.1 against $0.39 for Gemini 3.1 Pro Preview across all ten prompts, measured in Krater. Both had one slow extended-thinking run on the hardest coding task.
Which is faster, Claude or Gemini?
Effectively tied: median answer times were 13.4s for Claude and 14.5s for Gemini across the ten prompts. Both spent about 100 seconds thinking through the rounding bug, far longer than the other models in the round.
Can I use Claude and Gemini in the same place?
Yes. Krater gives you Claude Fable 5.1, Gemini 3.1 Pro Preview and 500+ other models in one workspace, and the Model Arena sends one prompt to several models side by side, which is 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.
