Claude Fable 5.1 (max) vs DeepSeek V4.1 Flash (max)

Head-to-head on the Towards AI writing benchmark: same 10 real YouTube scripts, five runs each, scored blind by a three-family judge panel. Claude Fable 5.1 (max) leads overall, 89.7 to 86.8.

Claude Fable 5.1 (max)

#1 Elo 2290 · 89.7/100

DeepSeek V4.1 Flash (max)

#22 Elo 2085 · 86.8/100

Cost / script

$3.153 vs $0.012

Human baseline

90.2 Claude Fable 5.1 (max) falls below it · DeepSeek V4.1 Flash (max) falls below it

The verdict

Claude Fable 5.1 (max effort) has the stronger current result: #1 at 2289.7 Elo and 89.71 overall, compared with DeepSeek V4.1 Flash (max) at #22, 2085.1 Elo, and 86.75 overall. Their 95% Elo confidence intervals do not overlap, which supports the directional ordering (2229.00–2346.50 and 2037.20–2122.70). Claude Fable 5.1 (max effort) has its clearest metric edges in Length Adherence (94.83 versus 89.95) and YouTube Best Practices (88.99 versus 84.92). DeepSeek V4.1 Flash (max) does not lead an individual published metric in this pairing. At the measured run mix, Claude Fable 5.1 (max effort) costs $3.153 per article versus $0.012 for DeepSeek V4.1 Flash (max); DeepSeek V4.1 Flash (max) is the cheaper route. DeepSeek V4.1 Flash (max) is the open-weights option; Claude Fable 5.1 (max effort) is closed. On the current automated evidence, Claude Fable 5.1 (max effort) is the stronger default; DeepSeek V4.1 Flash (max) remains a defensible choice when its specific strengths, price, or deployment profile matter more than the headline rank.

Pick Claude Fable 5.1 (max effort) when you prioritize the stronger current board result, length adherence, and youtube best practices.
Pick DeepSeek V4.1 Flash (max) when you prioritize open weights, and lower measured cost.

Metric by metric

Blue bars: Claude Fable 5.1 (max). Orange bars: DeepSeek V4.1 Flash (max). Same 0–100 scale; the bold bar wins that metric.

Tone & Voice Match19% weight

89.3

87.4

Writing Craft & Clarity13% weight

89.2

87.3

Substance, Accuracy & Value15% weight

88.9

85.2

Continuity & Emotion14% weight

88.5

84.9

YouTube Best Practices12% weight

89.0

84.9

Hook Strength10% weight

90.2

88.9

Length Adherence8% weight

94.8

90.0

Slop Score (EQ-Bench + ours)5% weight

94.0

91.0

Visual Cue Quality4% weight

85.5

82.3

Everything else that differs

	Claude Fable 5.1 (max)	DeepSeek V4.1 Flash (max)
Overall / 100	89.7	86.8
Writing Elo	2290	2085
Run-to-run spread (± overall std)	3.870	6.940
Cost per script (USD)	3.153	0.012
Avg latency (s)	622.5	74.6
Open weights	No	Yes

Full scorecards: Claude Fable 5.1 (max) · DeepSeek V4.1 Flash (max). How scoring works: methodology.

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