Model Comparison
Claude Sonnet 5.5 vs GPT-5.6 Terra
Claude Sonnet 5.5 (max effort) leads GPT-5.6 Terra (ultra) by 487 Elo, and their 95% ranges sit 391 Elo apart. Among 78 models, each ranked by its best configuration, Claude Sonnet 5.5 is #2 and GPT-5.6 Terra is #13. Cost per script: $1.38 for Claude Sonnet 5.5 (max effort) and $0.275 for GPT-5.6 Terra (ultra).
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) for a script you'll publish, since $0.302 gets a setting 274 Elo above anything Terra reaches.
PickGPT-5.6 Terra
GPT-5.6 Terra (medium)
Pick GPT-5.6 Terra (medium) for the cheapest usable draft, because at $0.062 it ranks above both Sonnet settings in that price range.
The setting you run decides this one. At the top, Claude Sonnet 5.5 (max effort) leads GPT-5.6 Terra (ultra) by 487 Elo, with 95% ranges far apart: Sonnet is the #2 model of 78 and Terra the #13 model. At the cheap end, Terra comes out ahead. GPT-5.6 Terra (medium) ranks above both Claude Sonnet 5.5 (low) and Claude Sonnet 5.5 (medium), with separate ranges, and all three cost about six cents a script. For the cheapest usable draft, I'd take Terra. Past that, Terra doesn't have far to go: ultra adds 76 Elo over medium for about 4.4 times the cost, with overlapping ranges, so the board can't separate the two. Sonnet keeps climbing. At high it's already inside Terra's ultra range for $0.092, a third of the price, and xhigh clears Terra's best by 274 Elo for $0.302, about three cents more than ultra. Against Sonnet's best, Terra is within two points on substance and level on hooks. It's about four to five points back on tone and writing craft, and that's the part I can't fix quickly in an edit. I'd run Sonnet at xhigh.
Disclosure: Claude Sonnet 5.5 and GPT-5.6 Terra each come from the same lab as one of the judges (Claude Opus 5.5 and GPT-6.1 Sol). 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 GPT-5.6 Terra, 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 Sonnet 5.5 (xhigh) | 2348 | 2304 to 2383 | 83.2 | $0.302 | 3.1 min | #10 |
| GPT-5.6 Terra (ultra) | 2074 | 2035 to 2113 | 81.4 | $0.275 | 8.0 min | #25 |
| Claude Sonnet 5.5 (high) | 2040 | 1984 to 2087 | 81.0 | $0.092 | 1.0 min | #27 |
| GPT-5.6 Terra (medium) | 1998 | 1952 to 2041 | 80.7 | $0.062 | 1.4 min | #33 |
| 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) leads GPT-5.6 Terra (ultra) by 487 Elo, and their 95% ranges do not overlap (2504 to 2614 against 2035 to 2113), which is strong evidence for that order.
- Lowest Thinking Levels Head to Head. At their lowest thinking levels, GPT-5.6 Terra (medium) at Elo 1998 and $0.062 per script leads Claude Sonnet 5.5 (low) at Elo 1808 and $0.061 per script by 190 Elo. Their 95% ranges do not overlap.
- Same Level Name, Side by Side. At medium, the one level name both models use, GPT-5.6 Terra has the higher Writing Elo: 1998 against 1856. Their 95% ranges do not overlap there. Level names come from each provider, so the same name does not promise the same reasoning budget.
- Cheapest Claude Sonnet 5.5 Configuration Above GPT-5.6 Terra's Best. The cheapest Claude Sonnet 5.5 configuration with a higher Writing Elo than GPT-5.6 Terra (ultra), at Elo 2074 and $0.275 per script, is Claude Sonnet 5.5 (xhigh), at Elo 2348 and $0.302 per script. The two cost about the same per script.
- 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. GPT-5.6 Terra moves +76 Elo from medium to ultra, at about 4.4 times the cost per script.
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 eight of the nine metrics and GPT-5.6 Terra (ultra) on one. Weighted by each metric's share of the Writing Score, Tone & Voice Match does the most to put Claude Sonnet 5.5 (max effort) ahead, with a 3.6-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) | GPT-5.6 Terra (ultra) | |
|---|---|---|
| Score spread across drafts (±) | 1.22 | 1.38 |
| Lowest script score | 83.0 Script 10 | 79.8 Script 4 |
| Highest script score | 86.7 Script 9 | 83.0 Script 6 |
| Range across scripts | 3.7 | 3.2 |
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 GPT-5.6 Terra (ultra), and the higher score is in bold.
| Script | Claude Sonnet 5.5 (max effort) | GPT-5.6 Terra (ultra) | Gap |
|---|---|---|---|
| Script 1 opinion / warning explainer | 84.2 | 81.1 | +3.1 |
| Script 2 news-analysis / skeptical explainer | 84.8 | 82.1 | +2.7 |
| Script 3 personal roadmap / opinion | 84.0 | 82.5 | +1.5 |
| Script 4 short explainer | 85.0 | 79.8 | +5.2 |
| Script 5 news-analysis / opinion explainer | 84.8 | 82.2 | +2.6 |
| Script 6 founder announcement / personal origin story | 84.6 | 83.0 | +1.6 |
| Script 7 personal technical walkthrough / agentic workflow case study | 85.0 | 80.6 | +4.4 |
| Script 8 product release announcement / personal observation | 83.9 | 80.3 | +3.6 |
| Script 9 career guide / hiring analysis | 86.7 | 81.8 | +4.9 |
| Script 10 engineering process walkthrough / presentation adaptation | 83.0 | 80.6 | +2.4 |
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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