Standard Compute
Model comparison 2026

Claude Sonnet 5.5 vs DeepSeek V4 Flash

Claude Sonnet 5.5
Anthropic · Balanced · Proprietary
$4.40/1M · 1M ctx
DeepSeek V4 Flash
DeepSeek · Budget · Open weights
$0.42/1M · 1.0M ctx

Community vote

Pick a winner in each dimension. You can change your vote any time.

Output Quality
Correctness and depth of what it produces
Agentic Ability
Tool calls, instruction-following, and multi-step tasks
Speed
Tokens per second and time-to-first-token
Value for money
How much capability you get per dollar
Reliability
Consistent results: fewer refusals, loops and format breaks

Specs and pricing side by side

Spec
Sonnet 5.5
DeepSeek V4 Flash
Maker
Anthropic
DeepSeek
Blended price / 1M
$4.40
$0.42
Input / output
$2.00 in · $10 out / 1M tokens
$0.05 in · $1.28 out / 1M tokens
Context window
1M
1.0M
Open weights
No
Yes
Tool use
Yes
Yes
Reasoning
Yes
Yes
Output Quality
9.8
8.2
Agentic Ability
9.8
8.1
Speed
8.4
9.0
Value for money
8.8
10.0
Reliability
9.4
8.9

Pricing and capabilities synced from the OpenRouter catalogue. Scores are editorial (0–10).

Verdict: Sonnet 5.5 or DeepSeek V4 Flash?

Updated 2026-10-13

Choose Claude Sonnet 5.5 if you want the everyday default for coding agents, escalating to Opus 5.5 only for the hardest tasks. Choose DeepSeek V4 Flash if you want cheap, high-volume open-weight agent steps.

In our editorial scoring, Claude Sonnet 5.5 leads in 3 of five dimensions (output quality, agentic ability and reliability), while DeepSeek V4 Flash leads in 2. On price, Claude Sonnet 5.5 runs about $4.40 per 1M tokens (blended) and is proprietary; DeepSeek V4 Flash is about $0.42 and open-weight.

Where Sonnet 5.5 falls short
  • Artificial Analysis flags it as very verbose, which adds output tokens
  • Released September 2026, so its long-run track record is still short
Full Sonnet 5.5 breakdown →
Where DeepSeek V4 Flash falls short
  • Not for the hardest tasks
  • Quality below V4 Pro
Full DeepSeek V4 Flash breakdown →

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