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  5. Gemini 2.5 Flash Preview 05-20 (thinking)vsGPT-5 Pro
Updated Oct 2025

Gemini 2.5 Flash Preview 05-20 (thinking)vsGPT-5 Pro

Gemini 2.5 Flash Preview 05-20 (thinking) is cheaper than GPT-5 Pro at $0.15/M vs $15/M input tokens.

Gemini 2.5 Flash Preview 05-20 (thinking) and GPT-5 Pro compared across 7 shared prompts
SpecGemini 2.5 Flash Preview 05-20 (thinking)GPT-5 Pro
Input price$0.15/M tokens$15/M tokens
Output price$3.5/M tokens$120/M tokens
Context window1.0M tokens400K tokens
Weights—Closed
Free API (OpenRouter)NoNo
ReleasedMay 2025Oct 2025
Side by side

Same prompt, both answers

Opening lines from 3 of the 7 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
GPT-5 Pro650 words
Good to be here. I tried getting healthy, so I bought a smartwatch. Now my wrist is my manager. It vibrates every hour like, “Stand up.” I’m on a crowded bus like, “I’m standing inside three other people right now. Do you want me to levitate?” It reminds me to breathe. Thanks, watch. Incredible tip.
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.
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GPT-5 Pro88 words
I started labeling my leftovers “Biohazard.” Now nobody steals my lunch and the fridge is treated like a lab. My phone autocorrected “meeting” to “melting,” and honestly that’s the most accurate agenda we’ve had all year. I told my plants I’d water them tomorrow. They leafed me on read.
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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
GPT-5 Pro14 words
No. 9.11 is less than 9.9, because 9.9 = 9.90 and 9.11 < 9.90.
Read the full answer
Our Verdict
GPT-5 Pro
GPT-5 Pro
Gemini 2.5 Flash Preview 05-20 (thinking)
Gemini 2.5 Flash Preview 05-20 (thinking)Runner-up

Not enough votes to call it. On the specs, GPT-5 Pro has the edge: bigger model tier, newer.

Gemini 2.5 Flash Preview 05-20 (thinking) costs 34x less per token.

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
100× cheaper
Output
$3.50
34× cheaper
GPT-5 Pro
Input
$15.00
Output
$120.00

Gemini 2.5 Flash Preview 05-20 (thinking) is cheaper on both: 100× input, 34× output.

Where to run it

1 host

Gemini 2.5 Flash Preview 05-20 (thinking)

No hosts listed on OpenRouter.

GPT-5 Pro1 host
HostInOutContextUptime
OpenAI$15.00 in·$120.00 out·400k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 21 Sep 2026.

Writing DNA

Style Comparison

Similarity
60%

GPT-5 Pro uses 32.0x more hedging

Gemini 2.5 Flash Preview 05-20 (thinking)
GPT-5 Pro
70%Vocabulary65%
11wSentence Length15w
0.00Hedging0.32
4.2Bold0.0
7.3Lists2.9
0.00Emoji0.00
0.00Headings0.00
0.00Transitions0.01
Based on 3 + 11 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 GPT-5 Pro is developed by OpenAI. Gemini 2.5 Flash Preview 05-20 (thinking) has a 1.0M token context window vs GPT-5 Pro's 400K. You can compare their actual outputs across 7 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 GPT-5 Pro each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 7 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 GPT-5 Pro costs $15/M input tokens. Gemini 2.5 Flash Preview 05-20 (thinking) is $14.85/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 GPT-5 Pro 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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Same lab, same size, long tail

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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
GPT-5 Pro logo
GPT-5 Pro42 outputs, specs and price
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