Gemini 2.5 Flash Preview 05-20 (thinking) vs OpenAI o3

Compare Gemini 2.5 Flash Preview 05-20 (thinking) by Google AI against OpenAI o3 by OpenAI, tested across 12 shared challenges. Updated April 2026.

Which is better, Gemini 2.5 Flash Preview 05-20 (thinking) or OpenAI o3?

Gemini 2.5 Flash Preview 05-20 (thinking) and OpenAI o3 are both competitive models. Gemini 2.5 Flash Preview 05-20 (thinking) costs $0.15/M input tokens vs $10/M for OpenAI o3. Compare their real outputs side by side below.

Key Differences Between Gemini 2.5 Flash Preview 05-20 (thinking) and OpenAI o3

Gemini 2.5 Flash Preview 05-20 (thinking) is made by google while OpenAI o3 is from openai. On pricing, Gemini 2.5 Flash Preview 05-20 (thinking) costs $0.15/M input tokens vs $10/M for OpenAI o3.

Our Verdict
Gemini 2.5 Flash Preview 05-20 (thinking)
Gemini 2.5 Flash Preview 05-20 (thinking)
OpenAI o3
OpenAI o3

No community votes yet. On paper, these are closely matched - try both with your actual task to see which fits your workflow.

Gemini 2.5 Flash Preview 05-20 (thinking) is 11x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
96%

OpenAI o3 uses 26.0x more hedging

Gemini 2.5 Flash Preview 05-20 (thinking)
OpenAI o3
70%Vocabulary68%
11wSentence Length14w
0.00Hedging0.26
4.2Bold0.7
7.3Lists3.0
0.00Emoji0.00
0.00Headings0.38
0.00Transitions0.12
Based on 3 + 16 text responses
vs

Ask them anything yourself

Gemini 2.5 Flash Preview 05-20 (thinking)OpenAI o3

279 AI models invented the same fake scientist.

We read every word. 250 models. 2.14 million words. This is what we found.

AI Hallucination Index 2026
Free preview13 of 58 slides
FAQ

Common questions