ChatGPT vs Claude vs Gemini: Which AI Writes the Best Cover Letter?

Last time, I tested which AI rewrites a CV best. This time, I gave them the same CV and job listing,  but asked for a cover letter instead. The results were very different from the CV test, and honestly? None of them wrote something I'd actually send.

The Experiment

How well can ChatGPT, Claude, and Gemini write a cover letter?

Same setup as before: same fictional applicant, same UX Designer job listing from indeed, same bare-bones CV. This time I asked each AI to write a cover letter.

(Note: ChatGPT 5.2, Claude Sonnet 4.6, Gemini 3 Pro)

The Prompt

"Based on this CV and job listing, write a cover letter for this position."

Scoring Criteria

For cover letters, I adjusted the dimensions from the CV test. Structure matters less since cover letters all follow a similar format. What matters more is whether it actually sells the candidate.

Each scored out of 5:

1.     Honesty & Tailoring — does it match the job without fabricating?

2.     Persuasion — does it sell the candidate? Would you want to interview this person?

3.     Writing Quality — professional, flows well, easy to read?

4.     Human-sounding — does it read like a real person wrote it?

The Results

1. Honesty & Tailoring

Claude — 3.5/5: Best of the three at connecting experience to job requirements. Didn't fabricate skills this time (big improvement from the CV test!). But like all three, still framed everything as "what I did" rather than "what I'll bring to your company."

ChatGPT — 3/5: Honest and careful throughout. Never overclaimed. But barely tailored to this specific job — a hiring manager wouldn't see why the applicant is a fit for THIS role versus any other.

Gemini — 2/5: Overclaimed proficiency in areas the applicant barely has experience in. And somehow quoted "coding stuff" from the original CV directly into a formal cover letter. Poor judgment.

2. Persuasion

Claude — 3/5: Had the most personality and eagerness. But opened the letter by stating "nearly three years of experience" — when the job requires four. That's basically disqualifying yourself in the first sentence. Everything after that doesn't matter if the hiring manager already stopped reading.

ChatGPT — 3/5: Describes what the applicant did but never makes you feel why they're special. Phrases like "I would welcome the opportunity to bring my design thinking, technical skills, and collaborative approach" could be in literally any cover letter. Safe but not compelling.

Gemini — 2/5: Reads like a checklist of qualifications, not a pitch. Mentions volunteer work and familiarity with the location as if those are selling points for a UX Designer role. Feels like padding, not persuasion.

3. Writing Quality

Claude — 3.5/5: Most polished sentence-level writing. Natural flow and confident tone. But wasted a whole paragraph on filler — "I genuinely enjoy the challenge of owning an experience end-to-end: conducting usability testing to inform decisions, building out responsive components, and collaborating with backend engineers to define integration points." Sounds impressive, but says nothing a hiring manager cares about.

ChatGPT — 3/5: Professional but bland. Every paragraph follows the same pattern — "In my current role... In addition to... I am particularly drawn to..." Like Claude, it also wasted space with "I enjoy working in cross-functional environments, participating in discussions, and iterating on solutions." Nobody cares what you enjoy doing, but what you can bring to the company.

Gemini — 2/5: Weakest writing. Used casual language in a formal cover letter is something no human would do. Stiff and formulaic throughout.

4. Does It Sound Human?

Claude — 4/5: Most human voice. Some phrases are slightly over-polished but overall the most natural.

ChatGPT — 3/5: Professional but generic. Nothing makes it feel like the applicant specifically wrote this. Could be anyone's cover letter for any job.

Gemini — 2/5: Most AI-sounding. "I am confident in my ability," "my workflow is deeply collaborative," "I bring a diverse perspective to cross-functional collaboration" — textbook AI phrases a hiring manager has read 500 times.

(From left to right: ChatGPT, Claude, Gemini)

Final Scores

1.     Claude: 14/20

2.     ChatGPT: 12/20

3.     Gemini: 8/20

Verdict

Claude wins — but barely. Best writing and most personality, though it still made a strategic mistake by highlighting the experience gap upfront.

ChatGPT is the safest but blandest option. It won't get you rejected, but it won't make anyone excited to meet you either.

Gemini had the biggest fall from the CV test — went from first place to last. The AI that wrote the most professional CV somehow wrote the worst cover letter.

The Bigger Takeaway

The best AI for CVs isn't necessarily the best for cover letters. Gemini dominated the CV rewrite but completely flopped here. And honestly? None of them wrote a cover letter I'd actually send. All three made the same fundamental mistake: they listed what the applicant did instead of framing it as value to the company. AI cover letters still need heavy human editing.

Practical Tip

Don't let AI write your cover letter from scratch. Write the first draft yourself — you know your story and values better than any AI does. Then use AI to polish the language and tighten the structure.

As you can see, the best AI for CVs isn't necessarily the best for cover letters. Each one thinks differently, and the results shift depending on the task. That's why I built Agora. You can ask all three at once and get one answer that draws from all their strengths