I Spent $2,847 Testing Every AI Developer Tool So You Dont Have To — Only 3 Actually Replaced a Junior Engineer

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I Spent $2,847 Testing Every “AI Developer” Tool So You Don’t Have To — Only 3 Actually Replaced a Junior Engineer

After my Devin AI review went semi-viral, I got obsessed. I dropped $2,847 of my own money over 60 days testing 11 “AI software engineer” tools on a real production SaaS codebase (Next.js + Postgres, 38k LOC). Here’s the unfiltered truth nobody is telling you.

The TL;DR Leaderboard (real PRs merged, not demos)

• Cursor Composer + Claude 4.5 Sonnet — 87% of PRs merged with <1 revision. Cost: $40/mo. Winner.
• Devin AI — 23% merge rate. $500/mo. Great for greenfield, terrible at legacy.
• GitHub Copilot Workspace — 71% merge rate. $39/mo. Boring but reliable.
• The other 8? Burned $1,400+ on tools that couldn’t even run the test suite.

What actually happened on day 14

I gave each tool the same ticket: “Add Stripe subscription pause + resume + proration to billing flow.” Real ticket from a real backlog. Devin spent 4 hours and produced code that called a deprecated API from 2022. Cursor + Claude shipped a working PR in 38 minutes that I merged unchanged.

The 3 that actually replaced a junior

I’d hire a $7k/mo junior dev to do what these 3 do — and these cost $40-500/mo combined. Here’s the exact stack I now run:

1. Cursor Composer (planning + writing) — $40/mo
2. Codex CLI in tmux (long-running refactors) — $200/mo usage
3. Claude Code for review (catches what others miss) — $20/mo on Max plan

What’s NOT working (save your money)

Anything marketed as “fully autonomous.” It’s all theater. The tools that win are the ones that treat you as the brain and themselves as fast hands.

Want my exact prompts + Cursor rules file? Grab the free pack here.