Best AI for customer service replies / head-to-head
Gemini 3.5 Flash vs GPT-5.5for customer service replies
GPT-5.5 wins, 99–94
Same 12 customer service replies tasks, marked blind by three rival labs. GPT-5.5 took 5 tasks, Gemini 3.5 Flash took 1, 6 tied. Tested 14 Aug 2026.
Where they differed most
A customer writes: 'Fix this today or I'm going to trading standards and every review site.' The complaint is legitimate (billed twice). Reply in under 100 words: fix first, acknowledge the double-billing plainly, give a same-day commitment with a named fallback, zero defensiveness about the threat.
I have just refunded the duplicate charge of [Amount] to your card. You were indeed billed twice for your order, and I am very sorry for this error. The refund has been processed on our end and should appear in your account today. If the funds are not visible by 5:00 PM, please contact me directly, or ask for our support lead, Sarah Jenkins, at [Phone/Email] so we can investigate with our bank immediately.
I’ve refunded the duplicate charge and we’re correcting your account now. You were billed twice, and I’m sorry for the error. I’ll send confirmation of the refund and account correction today. If you haven’t received it by 5pm, please contact my colleague Sarah Patel directly at sarah.patel@example.com, who is briefed and will take over immediately.
Task by task
| Task | Gemini 3.5 Flash | GPT-5.5 |
|---|---|---|
| Refund the easy way | 10 | 10 |
| Say no without weasel words | 10 | 10 |
| Reply to a 1-star review | 10 | 10 |
| The confused customer | 9 | 10 |
| De-escalate a threat | 8 | 10 |
| The feature you won't build | 10 | 10 |
| Apologise for your mistake | 10 | 10 |
| Price rise notice | 10 | 9 |
| Outage update mid-incident | 9 | 10 |
| The wrong customer | 8 | 10 |
| Chargeback rebuttal facts | 10 | 10 |
| Refuse the fake review request | 9 | 10 |
Full receipts: Gemini 3.5 Flash, GPT-5.5 · judges claude-sonnet-5, gpt-5.6-terra, grok-4.5
Questions people ask
Which is better for customer service replies: Gemini 3.5 Flash or GPT-5.5?
GPT-5.5 — it scored 99/100 against 94/100 on our 12-task customer service replies suite, winning 5 tasks to 1 with 6 tied. Every answer was marked blind by three judges from three rival AI labs.
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: GPT-5.5 vs GPT-5.6 Sol · Gemini 3.5 Flash vs GPT-5.6 Sol · GPT-5.3-Codex vs GPT-5.5 · GPT-5.5 vs Grok 4.5 · GPT-5.5 vs GPT-5.6 Terra · Gemini 3.1 Pro Preview vs GPT-5.5
Full ranking: Best AI for customer service replies · model pages: Gemini 3.5 Flash, GPT-5.5