AI Models · April 10, 2026 · 10 min read
DeepSeek R2 vs. Claude Sonnet 3.7 for Long-Form SEO Content: A 90-Day Test
We ran both models across 480 niche articles on identical topic clusters and measured keyword density, Yoast score, bounce rate, and average position after 90 days. The results surprised us — and changed how we default model selection in new schedules.
By FluxWriter Team
The setup
We built two parallel WordPress sites in the same niche (mid-tier home improvement), connected each to FluxWriter, and queued 240 posts on each site from the same 30 topic clusters. One site ran DeepSeek R2 exclusively; the other ran Claude Sonnet 3.7. Same briefs, same internal-link rules, same publish cadence (3/day).
Headline numbers after 90 days
| Metric | DeepSeek R2 | Claude Sonnet 3.7 |
|---|---|---|
| Avg. Yoast score (out of 100) | 78 | 91 |
| Avg. word count | 1,420 | 1,680 |
| Posts ranking top 10 (any cluster keyword) | 64 | 112 |
| Avg. bounce rate | 71% | 58% |
| Cost per post (USD) | $0.14 | $0.62 |
Where DeepSeek wins
DeepSeek R2 is 4x cheaper and produces clean, factually careful prose. For commodity informational content — "what is X," "how does Y work" — it's genuinely fine, and the cost difference compounds fast at scale.
Where Claude pulls ahead
Three places, consistently:
- Following structural instructions. If the brief says "include a comparison table and a 3-question FAQ," Claude does it ~95% of the time; DeepSeek does it ~60%.
- Internal linking. Claude weaves the supplied internal links into natural anchor text. DeepSeek tends to dump them in a "Related" list at the end.
- Hooks and intros. Bounce rate is the giveaway — Claude's intros keep readers on page noticeably longer.
What we changed in FluxWriter after this test
New schedules now default to Claude Sonnet for pillar posts and let users opt into DeepSeek for satellites. The cost-per-cluster only goes up ~25%, but the ranking outcomes were too lopsided to ignore.
Run your own test on your niche before you commit either way — but don't pick on price alone.