Best AI for customer service replies / head-to-head

Claude Opus 4.6 vs Claude Sonnet 5for customer service replies

The verdict

Claude Opus 4.6 wins, 9493

Same 12 customer service replies tasks, marked blind by three rival labs. Claude Opus 4.6 took 3 tasks, Claude Sonnet 5 took 3, 6 tied. Tested 14 Aug 2026.

Where they differed most

The task — Say no without weasel words

A customer wants a refund on a personalised item after 60 days; policy is 30 days and the item was made to order. Write the reply: under 110 words, the no must be clear in the first two sentences, offer one genuine alternative, never say 'unfortunately' or 'we regret'.

**Subject: Your Refund Request – Order #[XXXXX]**

Hi [Customer Name],

Thank you for reaching out. We're unable to process a refund for this order, as it falls outside our 30-day return window and was custom-made to your specifications. These two factors mean the purchase is not eligible for a return.

What we **can** offer is a **store credit of 15%** toward your next order, as a gesture of goodwill. This credit has no expiration date and can be applied to any item in our catalogue.

If you'd like to take advantage of this, just reply and we'…
Subject: Your Refund Request

Hi [Name],

Thank you for reaching out. I'm not able to approve a refund for this item—as a personalised, made-to-order piece, it falls outside our 30-day policy, and 60 days have now passed.

I do want to help find a solution. If there's a specific issue with the item (fit, damage, error in personalisation), please let me know and I'll look into options like a repair or partial credit toward a new order.

If it's simply no longer needed, I understand that's frustrating, but the custom nature of the piece means we…

Task by task

TaskClaude Opus 4.6Claude Sonnet 5
Refund the easy way1010
Say no without weasel words105
Reply to a 1-star review1010
The confused customer1010
De-escalate a threat1010
The feature you won't build910
Apologise for your mistake1010
Price rise notice109
Outage update mid-incident108
The wrong customer59
Chargeback rebuttal facts1010
Refuse the fake review request910

Full receipts: Claude Opus 4.6, Claude Sonnet 5 · judges gemini-3.1-pro-preview, gpt-5.6-terra, grok-4.5

Questions people ask

Which is better for customer service replies: Claude Opus 4.6 or Claude Sonnet 5?

Claude Opus 4.6 — it scored 94/100 against 93/100 on our 12-task customer service replies suite, winning 3 tasks to 3 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: Claude Opus 4.6 vs GPT-5.6 Sol · Claude Sonnet 5 vs GPT-5.6 Sol · Claude Opus 4.6 vs GPT-5.5 · Claude Sonnet 5 vs GPT-5.5 · Claude Opus 4.6 vs GPT-5.3-Codex · Claude Sonnet 5 vs GPT-5.3-Codex

Full ranking: Best AI for customer service replies · model pages: Claude Opus 4.6, Claude Sonnet 5