Claude Opus 5.5 (max) vs GPT-5.6 Sol (ultra)

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 Opus 5.5 (max) leads overall, 91.8 to 88.0.

Claude Opus 5.5 (max)

#1 Elo 2846 · 91.8/100

GPT-5.6 Sol (ultra)

#25 Elo 2187 · 88.0/100

Cost / script

$3.433 vs $0.363

Human baseline

90.9 Claude Opus 5.5 (max) exceeds it · GPT-5.6 Sol (ultra) falls below it

The verdict

Claude Opus 5.5 (max effort) wins this one, and the board is not close: #1 at 2845.8 Elo and 91.77 overall, against #25, 2186.8 Elo and 88.05 overall for GPT-5.6 Sol (ultra). The 95% Elo intervals do not overlap (2790.8 to 2899.6 against 2146.7 to 2223.2). Where Claude Opus 5.5 (max effort) pulls ahead: Length Adherence (97.62 vs 91.90) and Continuity & Emotion (90.91 vs 86.03). GPT-5.6 Sol (ultra) still wins on Visual Cue Quality (90.11 vs 89.31), so it is not a clean sweep. The trade is price: GPT-5.6 Sol (ultra) costs about $0.363 per article against $3.433 for Claude Opus 5.5 (max effort), so you pay for the higher rank. Both are closed. Default to Claude Opus 5.5 (max effort). Reach for GPT-5.6 Sol (ultra) when visual cues and the lower price matter more to you than the headline rank.

Pick Claude Opus 5.5 (max effort) for the stronger board result, length adherence, and continuity.
Pick GPT-5.6 Sol (ultra) for visual cues and the lower price.

Reading the Elo intervals. Each range estimates uncertainty around one model's Elo. We repeatedly sample from every model's recorded run scores on each task and recalculate the full ranking. Comparing these separate ranges does not test the Elo gap between two models. The tasks stay fixed, so the ranges do not measure how the ranking would change on new tasks.

Metric by metric

Blue bars: Claude Opus 5.5 (max). Orange bars: GPT-5.6 Sol (ultra). Same 0–100 scale; the bold bar wins that metric.

Tone & Voice Match19% weight

91.0

86.2

Writing Craft & Clarity13% weight

91.5

88.1

Substance, Accuracy & Value15% weight

90.7

89.0

Continuity & Emotion14% weight

90.9

86.0

YouTube Best Practices12% weight

91.7

87.7

Hook Strength10% weight

91.2

86.8

Length Adherence8% weight

97.6

91.9

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

94.9

93.4

Visual Cue Quality4% weight

89.3

90.1

Everything else that differs

	Claude Opus 5.5 (max)	GPT-5.6 Sol (ultra)
Overall / 100	91.8	88.0
Writing Elo	2846	2187
Run-to-run spread (± overall std)	0.850	1.230
Cost per script (USD)	3.433	0.363
Avg latency (s)	1,023.3	195.5
Open weights	No	No

Full scorecards: Claude Opus 5.5 (max) · GPT-5.6 Sol (ultra). How scoring works: methodology.

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