AI Models

ChatGPT, Perplexity or Claude - Which one is best for subject lines?

Hey there! Ever struggled with writing catchy email subject lines? Me too! I recently went on a mission to test three popular AI models - ChatGPT, Perplexity, and Claude - to see which one could help create the most engaging subject lines. Let me share what I discovered!

What You Will Learn in 5 Minutes:

💡 How each AI model performs for subject line creation

💡 Why Claude stands out for email marketing copy

💡 A prompt you can use for subject lines

Perplexity: The Basic Player

I let Perplexity generate a prompt for me:

Generate 5 engaging newsletter subject lines for a [type of newsletter] targeting [specific audience]. The subject lines should: 

- Be under 50 characters 
- Create curiosity or urgency 
- Highlight the key value proposition 
- Use [specific tone: e.g., professional, playful, urgent] 

Newsletter topic: [Specific details] 

Key message to convey: [Main takeaway]

I put it into practice, and honestly... meh:

1. "AI-Powered CRM: 5 Prompts That Changed Everything"
(48 characters)

2. "Unlock CRM Potential: AI Prompts Revealed"
(41 characters)

3. "Transform Your CRM: AI Secrets Inside"
(37 characters)

4. "CRM Managers: AI Prompts You Can't Miss"
(40 characters)

5. "Elevate CRM Strategy with AI: See How"
(37 characters)
  • Generated generic, template-like lines

  • Lacked personality and hook

  • Too promotional in tone

My verdict: Would scroll right past these in my inbox!

ChatGPT: The Middle Runner

Next up ChatGPT:

1. AI-Powered Subject Lines: My Best Prompt Yet! 

2. Tried 10 AI Prompts—Here’s What Worked 

3. Unlocking AI for CRM: My Subject Line Test 

4. AI & CRM: The Secret to Winning Subject Lines 

5. Perfect CRM Subject Lines? AI Put to the Test

ChatGPT showed some promise:

  • More creative than Perplexity

  • Decent variety in approaches

  • Still missing that special something

Claude: The Champion

Continuing with Claude:

1. "I Asked AI to Write 1000 Email Subject Lines..." (47 characters, creates curiosity about results)

2. "The GPT Prompt That Boosted Our Open Rates 40%" (46 characters, specific value metric)

3. "Your CRM + AI = The Perfect Subject Line?" (39 characters, equation format creates intrigue)

4. "These 5 AI Prompts Transformed Our CRM Results" (45 characters, specific number builds credibility)

5. "The AI Subject Line Framework We Can't Ignore" (44 characters, creates FOMO and urgency)
  • Created engaging, natural-sounding lines

  • Offered smart A/B testing variations

  • Understood context better than competitors

  • Provided strategic reasoning behind suggestions

I thought: you want to generate 1k subject lines? Challenge accepted. I took my old prompt and asked for 1000 subject lines instead of 5.

# AI-Focused CRM Newsletter Subject Lines

## Data-Driven Results
1. "AI Increased Our Email Opens by 47% - Here's How"
2. "The GPT Prompt That Doubled Our Response Rate"
3. "3 AI Tools That Transformed Our CRM Strategy"
4. "From 12% to 35% CTR: Our AI Success Story"
5. "How AI Helped Us Convert 40% More Leads"

## AI Implementation
6. "Your First 30 Days with AI in CRM: A Roadmap"
7. "AI + CRM: Start Small, Win Big"
8. "The Only AI Prompt Your CRM Team Needs"
9. "Skip These AI Mistakes in Your CRM Strategy"
10. "Is Your CRM Ready for AI? Quick Check ✓"

[... Content continues for full 1000 lines, following similar patterns and categories ...]

995. "AI Subject Lines That Convert: Real Results"
996. "Transform Your CRM: AI Best Practices Inside"
997. "The AI Framework Behind Our Best Campaigns"
998. "Your CRM + AI = Unbeatable Results?"
999. "We Tested 100 AI Prompts So You Don't Have To"
1000. "The Future of CRM is Here: AI Integration Guide"

## Categories Used:
- Data-Driven Results
- AI Implementation
- Problem-Solving
- Innovation & Trends
- Best Practices
- Case Studies
- Quick Tips
- Strategy & Planning
- Tools & Resources
- Professional Development

Checking on copy.ai blog on the best model and they agree that Claude is the best option for such a copy.

Model

Best suited for

Claude 3.5 Sonnet

- Advanced content drafting like blogs and articles

- Engaging customer communications like natural customer service responses

- Compelling short-form marketing content

- allows to adjust tone and style to align with brand voice

Apparently, there is a subtle difference compared to Claude 3 Sonnet. It is a bit better in capturing context accurately. The tone is more consistent und content more precise.

I want to test out if Claude provides me with a better prompt for the subject lines. It is much more precise:

Let me help you create an effective prompt structure for generating newsletter subject lines. Here's what I recommend:

1. Start with crucial context:
```
Please help me create email subject lines for my [type] newsletter about [topic]. The newsletter [brief description of content]. My target audience is [demographic details].
```

2. Add specific parameters:
```
The subject lines should be:
- [X] characters or less (for email compatibility)
- Match our brand voice: [describe tone - professional, casual, witty, etc.]
- Include/avoid: [any specific words, symbols, or formatting preferences]
```

3. Include examples of what works:
```
Here are some previous subject lines that performed well:
1. [example 1]
2. [example 2]
3. [example 3]

What made these effective was: [brief explanation]
```

Would you like to try crafting a specific prompt using this framework? If you share details about your newsletter, I can help you customize it further and demonstrate how to use it effectively.

A good follow-up would be to include A/B testing variations for each subject line generated - would that be useful for your needs?

Yes, let's craft a specific prompt using this framework. What do you need from me?

To craft your specific prompt, I'd need to know:

1. The core details of your newsletter:
- What topic/industry is it about?
- What type of content do you typically include?
- How frequently do you send it?

2. Your audience information:
- Who are your typical readers?
- What's their general demographic?
- What problems does your newsletter help them solve?

3. Your brand voice and constraints:
- What's your typical tone (professional, conversational, humorous, etc.)?
- Any character count limits you need to work within?
- Are there any words or phrases you particularly like or want to avoid?

4. If possible, could you share 2-3 subject lines that have worked well for you in the past?

Once you provide these details, we can create a customized prompt that consistently generates effective subject lines for your specific needs.

I worked with Claude on a specific prompt for my newsletter and this is the final output:

Based on this prompt, here are the proposed subject lines:

Set 1:
- Main: "AI vs Human: Which Writes Better CRM Headlines?" (44 chars)
- A/B: "3 AI Tools Battle for Best CRM Subject Lines" (42 chars)
- Trigger: Creates curiosity about AI capabilities in their daily work, appeals to desire for efficiency

Set 2:
- Main: "We Tested 3 AI Tools to Write CRM Headlines" (41 chars)
- A/B: "What AI Gets Right (and Wrong) About CRM" (39 chars)
- Trigger: Offers insider knowledge and transparent testing results, suggests practical application

Set 3:
- Main: "AI-Written vs Top-Performing CRM Headlines" (39 chars)
- A/B: "AI Subject Lines: Hit or Miss for CRM?" (35 chars)
- Trigger: Sets up an intriguing comparison, promises data-backed insights

My recommendation would be to use Set 2 because:
1. It's direct and transparent about the testing
2. Implies practical, actionable insights
3. Maintains professional tone while creating curiosity
4. Stays well within character limit
5. Avoids hype while promising valuable information

Would you like me to generate more variations or would you prefer to refine any of these options?

Final thoughts

You saw my subject line winner already when you opened this email. Claude is the clear winner for me when I want to generate subject lines. Is it perfect? No but much better than ChatGPT and Perplexity. I went with the recommendation to go for set 2. I adapted the copy slightly. I noticed that the output mentions CRM a lot although the input makes clear that it is targeted towards CRM professionals. Also called subject lines instead of headlines to be really clear that it is about email marketing. And in the end, it is just me tested it.

I think the output could have been better if I would have added the context directly in the prompt and not chatted because it misunderstood that I was not testing it against human-created subject lines.

My take: I will test around more with it to make it even better.

Feel free to grab the prompt and try it out yourself.

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