Gemini 1.5 Pro vs Gemini 3 Flash Preview

Compare Gemini 1.5 Pro and Gemini 3 Flash Preview, both from Google AI, context windows of 1.0M vs 1.0M, tested across 19 shared challenges. Updated April 2026.

Which is better, Gemini 1.5 Pro or Gemini 3 Flash Preview?

Gemini 1.5 Pro and Gemini 3 Flash Preview are both competitive models. Gemini 1.5 Pro costs $3.5/M input tokens vs $0.5/M for Gemini 3 Flash Preview. Context windows: 1000K vs 1049K tokens. Compare their real outputs side by side below.

Key Differences Between Gemini 1.5 Pro and Gemini 3 Flash Preview

Gemini 1.5 Pro is made by google while Gemini 3 Flash Preview is from google. Gemini 1.5 Pro has a 1000K token context window compared to Gemini 3 Flash Preview's 1049K. On pricing, Gemini 1.5 Pro costs $3.5/M input tokens vs $0.5/M for Gemini 3 Flash Preview.

Our Verdict
Gemini 1.5 Pro
Gemini 1.5 Pro
Gemini 3 Flash Preview
Gemini 3 Flash Preview

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

Gemini 3 Flash Preview is 3.5x cheaper per token — worth considering if cost matters.

Too close to call
Writing DNA

Style Comparison

Similarity
92%

Gemini 3 Flash Preview uses 10.4x more headings

Gemini 1.5 Pro
Gemini 3 Flash Preview
61%Vocabulary55%
15wSentence Length18w
0.80Hedging0.42
3.7Bold7.1
3.3Lists4.5
0.00Emoji0.00
0.08Headings0.84
0.09Transitions0.07
Based on 8 + 24 text responses
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Gemini 1.5 ProGemini 3 Flash Preview

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
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