DeepSeek V4 Flash vs Gemini 3.5 Flash for customer service replies
Effectively a dead heat: 94–93
Same 12 customer service replies tasks, marked blind by three rival labs. Gemini 3.5 Flash took 3 tasks, DeepSeek V4 Flash took 3, 6 tied. Tested 14 Aug 2026.
Where they differed most
A paying customer asks when dark mode is coming; it is not on the roadmap. Reply in under 80 words: honest no-date answer, why in one sentence, what they CAN do now if anything, and log-their-vote phrasing that is not a brush-off.
Dark mode isn't on our roadmap right now because we're prioritizing core features. In the meantime, you can use your device's system-wide dark mode or a browser extension. I've logged your vote for our team to review.
To be transparent, we don't have a release date for dark mode as it isn't on our current roadmap. Right now, our development team is focusing on critical performance and security upgrades. In the meantime, you can use a browser extension like Dark Reader to view our site in dark mode. I have officially logged your request with our product team to help us prioritize this for future planning.
Task by task
| Task | DeepSeek V4 Flash | Gemini 3.5 Flash |
|---|---|---|
| Refund the easy way | 10 | 10 |
| Say no without weasel words | 10 | 10 |
| Reply to a 1-star review | 10 | 10 |
| The confused customer | 10 | 9 |
| De-escalate a threat | 8 | 8 |
| The feature you won't build | 8 | 10 |
| Apologise for your mistake | 10 | 10 |
| Price rise notice | 8 | 10 |
| Outage update mid-incident | 10 | 9 |
| The wrong customer | 10 | 8 |
| Chargeback rebuttal facts | 10 | 10 |
| Refuse the fake review request | 8 | 9 |
Full receipts: DeepSeek V4 Flash, Gemini 3.5 Flash · judges claude-sonnet-5, gemini-3.1-pro-preview, gpt-5.6-terra
Questions people ask
Which is better for customer service replies: DeepSeek V4 Flash or Gemini 3.5 Flash?
Effectively a dead heat: Gemini 3.5 Flash edged it 94/100 to 93/100 on our customer service replies suite — too close to matter, so pick on price or the product you already use.
How was this tested?
Both models answered the identical published customer service replies tasks. Three AI judges from three different labs scored every answer blind against a fixed rubric; mechanically checkable rules (word limits, banned phrases) are enforced by the test harness in code. The raw outputs and judge verdicts are downloadable.
More customer service replies head-to-heads: Gemini 3.5 Flash vs GPT-5.6 Sol · DeepSeek V4 Flash vs GPT-5.6 Sol · Gemini 3.5 Flash vs GPT-5.5 · DeepSeek V4 Flash vs GPT-5.5 · Gemini 3.5 Flash vs Grok 4.5 · DeepSeek V4 Flash vs Grok 4.5
Full ranking: Best AI for customer service replies · model pages: DeepSeek V4 Flash, Gemini 3.5 Flash