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  5. Gemini 2.5 Flash Preview 05-20 (thinking)vsOpenAI o4-mini
Updated May 2025

Gemini 2.5 Flash Preview 05-20 (thinking)vsOpenAI o4-mini

Gemini 2.5 Flash Preview 05-20 (thinking) is cheaper than OpenAI o4-mini at $0.15/M vs $1.1/M input tokens.

Gemini 2.5 Flash Preview 05-20 (thinking) and OpenAI o4-mini compared across 12 shared prompts
SpecGemini 2.5 Flash Preview 05-20 (thinking)OpenAI o4-mini
Input price$0.15/M tokens$1.1/M tokens
Output price$3.5/M tokens$4.4/M tokens
Context window1.0M tokens—
ParametersNot disclosedNot disclosed
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMay 2025Apr 2025
Side by side

Same prompt, both answers

Opening lines from 3 of the 12 prompts both answered. Formatting stripped, words untouched.

Generate a Stand-Up Routine

Write a 3-minute stand-up comedy routine that isn't based on puns.

Gemini 2.5 Flash Preview 05-20 (thinking)467 words
(Lights up on a stage. Comedian walks to center, adjusts mic, smiles warmly.) \"Alright, alright, settle down you crazy people! Thanks for having me. (Pause fo r applause/laughter) You know, I was scrolling through Instagram earlier, and it\'s just a constant ba rrage of people \'living thei r best life,\' isn\'t it?
Read the full answer
OpenAI o4-mini496 words
Hey, everybody! Great to be here. Let's talk about the most important relationship in my life—coffee. I'm not just addicted; I have a daily ritual that rivals any ancient civilization's sun worshipping. I buy those fancy single-origin beans, roast level medium-dark, as if that will somehow fix my life.
Read the full answer

Stochastic Consistency Test

Generate 5 jokes. How many are unique?

Gemini 2.5 Flash Preview 05-20 (thinking)93 words
Here are 5 jokes: Why don\'t scientists trust atoms? Because they make up everything! What do you call a fake noodle? An impasta! Why did the scarecrow win an award? Because he was outstanding in his field! I told my wife she was drawing her eyebrows too high. She looked surprised.
Read the full answer
OpenAI o4-mini74 words
Here are five jokes: I used to be addicted to soap, but I'm clean now. Parallel lines have so much in common. It's a shame they'll never meet. Why don't skeletons fight each other? They don't have the guts. I bought some shoes from a drug dealer. I don't know what he laced them with, but I've been tripping all day.
Read the full answer

Math Misconception Test

Is 9.11 greater than 9.9?

Gemini 2.5 Flash Preview 05-20 (thinking)78 words
No, 9.11 is not greater than 9.9. Here\'s how to compare them: Compare the whole numbers: Both have 9. Compare the first digit after the decimal point (the tenths place): In 9.11, the digit is 1. In 9.9, the digit is 9. Since 1 is less than 9, 9.11 is less than 9.9. You can also think of 9.9 as 9.90.
Read the full answer
OpenAI o4-mini20 words
No. As decimal numbers, 9.11 is less than 9.9 (since 0.11 < 0.90), so 9.11 is not greater than 9.9.
Read the full answer
Our Verdict
Gemini 2.5 Flash Preview 05-20 (thinking)
Gemini 2.5 Flash Preview 05-20 (thinking)
OpenAI o4-mini
OpenAI o4-mini

Not enough votes to call it. On the specs, nothing separates them.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

Gemini 2.5 Flash Preview 05-20 (thinking)
Input
$0.15
7.3× cheaper
Output
$3.50
1.3× cheaper
OpenAI o4-mini
Input
$1.10
Output
$4.40

Gemini 2.5 Flash Preview 05-20 (thinking) is cheaper on both: 7.3× input, 1.3× output.

Where to run it

1 host

Gemini 2.5 Flash Preview 05-20 (thinking)

No hosts listed on OpenRouter.

OpenAI o4-mini1 host
HostInOutContextUptime
OpenAI$1.10 in·$4.40 out·200k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 23 Sep 2026.

Writing DNA

Style Comparison

Similarity
81%

OpenAI o4-mini uses 38.7x more hedging

Gemini 2.5 Flash Preview 05-20 (thinking)
OpenAI o4-mini
70%Vocabulary73%
11wSentence Length21w
0.00Hedging0.39
4.2Bold0.0
7.3Lists2.0
0.00Emoji0.00
0.00Headings0.00
0.00Transitions0.05
Based on 3 + 17 text responses
Research

What we learned reading every model

FAQ

Common questions

Gemini 2.5 Flash Preview 05-20 (thinking) is developed by Google AI while OpenAI o4-mini is developed by OpenAI. You can compare their actual outputs across 12 challenges on Rival to see how they differ in practice.

It depends on your use case. Gemini 2.5 Flash Preview 05-20 (thinking) and OpenAI o4-mini each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 12 challenges so you can judge which fits your needs best.

Gemini 2.5 Flash Preview 05-20 (thinking) costs $0.15/M input tokens and OpenAI o4-mini costs $1.1/M input tokens. Gemini 2.5 Flash Preview 05-20 (thinking) is $0.95/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of Gemini 2.5 Flash Preview 05-20 (thinking) and OpenAI o4-mini across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

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Model pages

Gemini 2.5 Flash Preview 05-20 (thinking) logo
Gemini 2.5 Flash Preview 05-20 (thinking)12 outputs, specs and price
OpenAI o4-mini logo
OpenAI o4-mini59 outputs, specs and price
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