Model Comparison
Claude Sonnet 5.5 vs Claude Fable 5.1
Too close to call: the best configurations, Claude Sonnet 5.5 (max effort) and Claude Fable 5.1 (max effort), are 8 Elo apart, and their 95% ranges overlap. Among 78 models, each ranked by its best configuration, Claude Sonnet 5.5 is #2 and Claude Fable 5.1 is #3. Cost per script: $1.38 for Claude Sonnet 5.5 (max effort) and $3.56 for Claude Fable 5.1 (max effort).
Last updated , from board data generated at 01:13 UTC.
Picks and Verdict
PickClaude Sonnet 5.5
Claude Sonnet 5.5 (xhigh)
Pick Claude Sonnet 5.5 (xhigh) as the setting to run most days, since at $0.302 a script the board can't separate it from Claude Fable 5.1 (high) at $1.85.
PickClaude Fable 5.1
Claude Fable 5.1 (max effort)
Pick Claude Fable 5.1 (max effort) if tone is what you edit most, since it edges Sonnet's best there by about a point and finishes in 12.3 minutes.
At the top, the board can't pick between these two, so price decides it. Claude Sonnet 5.5 (max effort) and Claude Fable 5.1 (max effort) sit 8 Elo apart with overlapping ranges, making Sonnet the #2 model of 78 and Fable the #3 model. Sonnet gets there for $1.38 a script, and Fable costs about two and a half times as much. One level down, the same thing happens: Claude Sonnet 5.5 (xhigh) at $0.302 overlaps Claude Fable 5.1 (high) at $1.85, so Fable charges about six times as much for a result the board can't tell apart, and takes twice as long. Below xhigh, Sonnet falls off fast. At the level both call high, Fable leads by 312 Elo with separate ranges, and Sonnet's full climb from low to max effort is 753 Elo against 201 for Fable from high to max. Fable has a real case on voice: at max effort it edges Sonnet by about a point on tone, YouTube structure and hooks, and it finishes in 12.3 minutes against 14.3. I'd still default to Sonnet at xhigh and keep max effort for the scripts that matter.
Disclosure: both models come from the same lab as one of the four judges, Claude Opus 5.5. The other judges sit outside that lab, so neither is scored by its own lab alone (how the panel works). The judge analysis measures how much each judge favors its own lab.
How to Read the Writing Score, Writing Elo and 95% Ranges
Writing Score and Writing Elo. The Writing Score (0 to 100) is the weighted average of the nine metric scores: seven from the judges, Length Adherence from code and the Slop Score half from each. The Writing Elo is a rating from pairwise comparisons: on each script, each configuration's average across its drafts is compared with every other configuration's, and gaps within the draft-to-draft variation count as draws. Elo rewards winning often, so the two can put configurations in a different order.
Elo ranges. Each 95% range shows how far a configuration's Elo could move if the drafts had come out slightly differently. It comes from resampling every configuration's recorded draft scores on each reference script and ranking again. Comparing two separate ranges does not test the Elo gap between them: ranges far apart are strong evidence for the order, and overlapping ranges do not mean a tie. The reference scripts stay fixed, so the ranges say nothing about new scripts. The methodology page has the full description.
All Thinking Levels of Both Models
Every ranked configuration of Claude Sonnet 5.5 and Claude Fable 5.1, scored on the same 10 scripts by the same four judges.
- Each row is one configuration: the model at one thinking level. The dot is its Writing Elo, a rating from pairwise comparisons of the scores on each script, and the bar is its 95% range: how far that Elo could move if the drafts had come out slightly differently.
- When two bars overlap, the board cannot order those two configurations. Bars far apart are strong evidence for the order.
- The table under the chart lists the same configurations in the same order and adds the Writing Score (the 0 to 100 consensus of the judges and code), cost, time and configuration rank (the place among all configurations on the board).
Shaded rows are the configurations chosen for the metric comparison below.
| Configuration | Writing Elo | 95% Range | Writing Score | Cost / Script | Time / Script | Configuration Rank |
|---|---|---|---|---|---|---|
| Claude Sonnet 5.5 (max effort) | 2561 | 2504 to 2614 | 84.6 | $1.38 | 14.3 min | #3 |
| Claude Fable 5.1 (max effort) | 2553 | 2513 to 2587 | 84.5 | $3.56 | 12.3 min | #4 |
| Claude Fable 5.1 (high) | 2352 | 2302 to 2403 | 83.4 | $1.85 | 6.3 min | #9 |
| Claude Sonnet 5.5 (xhigh) | 2348 | 2304 to 2383 | 83.2 | $0.302 | 3.1 min | #10 |
| Claude Sonnet 5.5 (high) | 2040 | 1984 to 2087 | 81.0 | $0.092 | 1.0 min | #27 |
| Claude Sonnet 5.5 (medium) | 1856 | 1812 to 1900 | 79.4 | $0.065 | 0.6 min | #47 |
| Claude Sonnet 5.5 (low) | 1808 | 1771 to 1843 | 78.9 | $0.061 | 0.7 min | #50 |
Cost is one script at the API list price of the route used, uncached and without judging. Time is the average for one accepted script, retries included.
Computed Findings Across Thinking Levels
Each finding is computed from the configurations above. Where two 95% ranges overlap, the board cannot order those two configurations.
- Best Configurations Head to Head. Claude Sonnet 5.5 (max effort) at Elo 2561 (range 2504 to 2614) and Claude Fable 5.1 (max effort) at Elo 2553 (range 2513 to 2587) have overlapping 95% ranges, so the board cannot separate the two best configurations.
- Lowest Thinking Levels Head to Head. At their lowest thinking levels, Claude Fable 5.1 (high) at Elo 2352 and $1.85 per script leads Claude Sonnet 5.5 (low) at Elo 1808 and $0.061 per script by 544 Elo. Their 95% ranges do not overlap.
- Same Level Name, Side by Side. Across the level names both models use, Claude Sonnet 5.5 leads at max; Claude Fable 5.1 leads at high. The 95% ranges do not overlap at high. Level names come from each provider, so the same name does not promise the same reasoning budget.
- Cheapest Claude Sonnet 5.5 Configuration Above Claude Fable 5.1's Best. The cheapest Claude Sonnet 5.5 configuration with a higher Writing Elo than Claude Fable 5.1 (max effort), at Elo 2553 and $3.56 per script, is Claude Sonnet 5.5 (max effort), at Elo 2561 and $1.38 per script. Their 95% ranges overlap, so the board cannot separate them. It costs less than the configuration it beats.
- Lowest to Highest Thinking Level. Claude Sonnet 5.5 moves +753 Elo from low to max effort, at about 23 times the cost per script. Claude Fable 5.1 moves +201 Elo from high to max effort, at about 1.9 times the cost per script.
Writing Elo at Each Shared Level Name
| Level | Claude Sonnet 5.5 | Claude Fable 5.1 | Gap | 95% Ranges |
|---|---|---|---|---|
| high | 2040 | 2352 | -312 | Separate |
| max | 2561 | 2553 | +8 | Overlap |
Gap is Claude Sonnet 5.5 minus Claude Fable 5.1 at the same level name, using each model's highest-rated configuration at that level.
Two Chosen Configurations Compared
Pick one configuration of each model to compare their metric scores, consistency across drafts and per-script scores. Each menu starts on the model's best configuration.
Scores by Metric
Claude Sonnet 5.5 (max effort) scores higher on five of the nine metrics and Claude Fable 5.1 (max effort) on three, with one tie. Weighted by each metric's share of the Writing Score, Substance, Accuracy & Value does the most to put Claude Sonnet 5.5 (max effort) ahead, with a 1.8-point lead on that metric. The weight beside each metric is its share of the Writing Score.
Consistency Across Drafts
| Claude Sonnet 5.5 (max effort) | Claude Fable 5.1 (max effort) | |
|---|---|---|
| Score spread across drafts (±) | 1.22 | 1.13 |
| Lowest script score | 83.0 Script 10 | 82.8 Script 10 |
| Highest script score | 86.7 Script 9 | 86.2 Script 9 |
| Range across scripts | 3.7 | 3.4 |
Spread is how much the Writing Score moves between a configuration's drafts, and lower is steadier. Green marks the better number in each row.
Scores by Script
Writing Score on each reference script. Gap is Claude Sonnet 5.5 (max effort) minus Claude Fable 5.1 (max effort), and the higher score is in bold.
| Script | Claude Sonnet 5.5 (max effort) | Claude Fable 5.1 (max effort) | Gap |
|---|---|---|---|
| Script 1 opinion / warning explainer | 84.2 | 83.3 | +0.9 |
| Script 2 news-analysis / skeptical explainer | 84.8 | 83.8 | +1.0 |
| Script 3 personal roadmap / opinion | 84.0 | 84.0 | 0.0 |
| Script 4 short explainer | 85.0 | 85.2 | -0.2 |
| Script 5 news-analysis / opinion explainer | 84.8 | 84.9 | -0.1 |
| Script 6 founder announcement / personal origin story | 84.6 | 85.0 | -0.4 |
| Script 7 personal technical walkthrough / agentic workflow case study | 85.0 | 85.3 | -0.3 |
| Script 8 product release announcement / personal observation | 83.9 | 84.7 | -0.8 |
| Script 9 career guide / hiring analysis | 86.7 | 86.2 | +0.5 |
| Script 10 engineering process walkthrough / presentation adaptation | 83.0 | 82.8 | +0.2 |
Scorecards and Thinking Pages
Each configuration name in the table above opens its own scorecard.
Compare With Another Model
Pick a second model. A pair with its own written match-up opens that page, and any other pair opens in the comparison tool.
Nearby Match-Ups by Best Writing Elo
Every configuration wrote five drafts for each of the same 10 briefs, from the same prompt. Generation was closed-book, with the prompt as the only source and no web search or other tools. Each judge scores every draft once: Claude Opus 5.5 at medium effort through the Claude Code subscription, GPT-6.1 Sol at medium reasoning through the Codex CLI, GLM 5.3 Flash through OpenRouter, and Jev 1.13, a typed judge from TypeSafe that answers each metric as a multiple-choice question. The channel's finished script is their reference for the voice, and it gets no score on the board itself.
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