DeepSeek R1 vs Claude 3.5 Sonnet: The Open Source Showdown
Can the new open-weights champion DeepSeek R1 dethrone Anthropic's coding king? We tested both on real-world coding tasks.
DeepSeek R1 vs Claude 3.5 Sonnet: The Open Source Showdown
For months, Claude 3.5 Sonnet has been the undisputed king of AI coding. It's fast, smart, and understands complex context better than GPT-4o.
But a new challenger has appeared: DeepSeek R1.
It's open-weights, massive, and claiming to beat Sonnet on coding benchmarks. We put both to the test in real-world development scenarios.
1. The Specs
Claude 3.5 Sonnet
- Provider: Anthropic
- Type: Closed Source (API)
- Strengths: Context window (200k), reasoning, instruction following
- Cost: ~$15/M input tokens
DeepSeek R1
- Provider: DeepSeek
- Type: Open Weights (Run locally or via API)
- Strengths: Math, logic, code generation
- Cost: ~$0.55/M input tokens (API) - 27x Cheaper!
2. Test 1: Refactoring a Legacy React Component
We gave both models a messy 300-line React class component and asked them to:
- Convert it to Functional Component
- Use TypeScript
- Implement React Query V5
Claude 3.5 Sonnet:
- Flawless conversion.
- Correctly identified 3 edge cases in the state logic.
- Code ran immediately without errors.
DeepSeek R1:
- Good conversion.
- Missed one obscure dependency in
useEffect. - Used slightly older React Query syntax initially, but corrected it after one prompt.
Winner: Claude (Narrowly), but DeepSeek was shockingly close.
3. Test 2: Writing complex SQL Queries
We asked for a complex PostgreSQL query involving 4 joins, a window function, and common table expressions (CTEs).
Claude 3.5 Sonnet:
- Valid SQL. Explained the logic well.
DeepSeek R1:
- Valid SQL. Actually optimized the query better by suggesting an index we didn't have.
Winner: Tie (DeepSeek for performance, Claude for explanation).
4. The "Agent" Factor
Here is the kicker: DeepSeek R1 is cheap.
If you are building an agent loop (like with Windsurf or Cursor) that runs 50 times to fix a bug:
- Claude Cost: $0.50
- DeepSeek Cost: $0.02
For autonomous agents that need to "think" for a long time, DeepSeek changes the economics completely.
Conclusion
Claude 3.5 Sonnet is still the smartest model for "one-shot" prompts where you need it to be right the first time.
DeepSeek R1 is the future of autonomous agents. Its low cost and high capability mean we can let agents loop, think, and retry until they solve the problem, without breaking the bank.
Recommendation
- Daily Driver: Continue using Claude 3.5 Sonnet in Cursor.
- Heavy Lifting: If you are running local agents or batch processing, switch to DeepSeek.