AI Copywriting Tools — We Tested 5 On The Same Product Brief. The Results Were Uncomfortable.
Jasper, Copy.ai, ChatGPT, Gemini, and Claude — same product brief, scored on persuasion, accuracy, and brand voice. One tool ranked above all others. The purpose-built ones didn't win.
Five copywriting tools. One product brief, identical across all of them. No editing, no cherry-picking — the raw first output from each, scored the same way. The results weren't close, and one tool underperformed badly enough that it's worth naming directly, not softening into "it depends."
The Brief And The Scoring
The task: write a product description for a mid-range wireless earbud, targeting people who care about sound quality over gimmicks, under 100 words. Scored on three criteria — persuasion (does it actually make you want the product), accuracy (does it avoid inventing specs that weren't provided), and brand voice retention (does it hold a consistent tone across multiple regenerations of the same prompt).
Where Each One Landed
Jasper produced confident, punchy marketing copy fast, clearly built for this exact use case — but leaned hard into generic superlatives ("game-changing," "unmatched") that read as filler rather than persuasion once you'd seen the pattern repeat across regenerations.
Copy.ai was the weakest of the five on accuracy, inventing a battery-life figure that wasn't in the brief and stating it as fact. That's the uncomfortable part — a tool built specifically for product copy produced the clearest hallucination of the test.
ChatGPT handled the brief competently, polished and structurally solid, but voice retention slipped across regenerations — ask for three variations and the tone drifted noticeably by the third.
Gemini was serviceable and safe, the most conservative of the five, which meant no hallucinations but also the least persuasive copy of the group — technically correct, emotionally flat.
Claude held the tightest brand voice across regenerations, avoided inventing any spec not in the brief, and wrote persuasion that leaned on the actual stated details rather than generic superlatives.
A tool built specifically for marketing copy produced the worst hallucination in the entire test. Purpose-built doesn't automatically mean more careful.
The Uncomfortable Part
The uncomfortable finding isn't which tool won — it's that the two tools marketed specifically as "AI copywriters" (Jasper, Copy.ai) underperformed the general-purpose assistants on accuracy and voice consistency. Specialization implied more reliability. It delivered less. That's worth sitting with before paying for a dedicated copywriting subscription on brand-name recognition alone.
The Winner
Claude ranked highest on all three criteria for this brief — no fence-sitting. ChatGPT is the strongest runner-up, particularly for fast first drafts where voice consistency across regenerations matters less. If accuracy and consistent brand voice are the priority, which they usually are for anything customer-facing, Claude is the call.
Run Your Own Five-Way Test
Take one real product or service description and run the identical brief through at least two tools — ideally one general-purpose and one purpose-built copy tool. Check both for invented specs before you trust either.
