Model Comparison
Claude Opus 5.5 vs GPT-5.6 Terra
Claude Opus 5.5 (max effort) leads GPT-5.6 Terra (ultra) by 714 Elo, and their 95% ranges sit 603 Elo apart. Even Claude Opus 5.5's lowest-rated configuration, Claude Opus 5.5 (low), ranks above GPT-5.6 Terra (ultra). Among 78 models, each ranked by its best configuration, Claude Opus 5.5 is #1 and GPT-5.6 Terra is #13. Cost per script: $2.58 for Claude Opus 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 Opus 5.5
Claude Opus 5.5 (low)
Pick Claude Opus 5.5 (low) if you were weighing Terra on price, since $0.243 a script buys a draft 419 Elo above Terra's best in 1.5 minutes.
PickGPT-5.6 Terra
GPT-5.6 Terra (medium)
Pick GPT-5.6 Terra (medium) for a lot of drafts at $0.062 each, since ultra costs about 4.4 times as much for a rating the board can't separate.
Claude Opus 5.5 (low) costs a little less than GPT-5.6 Terra (ultra), $0.243 against $0.275 a script, and that's the comparison that settles it for me. Opus at low ranks 419 Elo higher, with separate 95% ranges, and finishes in 1.5 minutes where Terra takes 8.0. Claude Opus 5.5 (xhigh) stretches that lead over Terra's best to 714 Elo, the #1 model of 78 against the #13 model. Terra's own ladder moves little. Ultra adds 76 Elo over medium for about 4.4 times the cost, and the two ranges overlap, so the board can't separate them. Medium even scores higher on Tone & Voice Match, 78.6 against 76.9. If I ran Terra, I'd keep it at medium. Opus has its own setting that only adds cost, max effort, at $2.58 with a range that overlaps xhigh's. Best against best, Terra holds up on substance, 1.6 points back, and trails by about six on voice. For a script that has to sound like me, voice decides it.
Disclosure: Claude Opus 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 Opus 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 Opus 5.5 (max effort) | 2788 | 2716 to 2845 | 85.9 | $2.58 | 17.5 min | #1 |
| Claude Opus 5.5 (xhigh) | 2788 | 2727 to 2851 | 85.8 | $1.00 | 6.7 min | #2 |
| Claude Opus 5.5 (high) | 2536 | 2486 to 2573 | 84.6 | $0.328 | 2.1 min | #5 |
| Claude Opus 5.5 (medium) | 2520 | 2469 to 2576 | 84.5 | $0.310 | 1.9 min | #6 |
| Claude Opus 5.5 (low) | 2493 | 2436 to 2536 | 84.3 | $0.243 | 1.5 min | #7 |
| GPT-5.6 Terra (ultra) | 2074 | 2035 to 2113 | 81.4 | $0.275 | 8.0 min | #25 |
| GPT-5.6 Terra (medium) | 1998 | 1952 to 2041 | 80.7 | $0.062 | 1.4 min | #33 |
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 Opus 5.5 (max effort) leads GPT-5.6 Terra (ultra) by 714 Elo, and their 95% ranges do not overlap (2716 to 2845 against 2035 to 2113), which is strong evidence for that order.
- Every Claude Opus 5.5 Configuration Ranks Higher. All five Claude Opus 5.5 configurations rank above both GPT-5.6 Terra configurations: the lowest-rated, Claude Opus 5.5 (low) at Elo 2493, still beats GPT-5.6 Terra (ultra) at Elo 2074. Their 95% ranges do not overlap.
- Lowest Thinking Levels Head to Head. At their lowest thinking levels, Claude Opus 5.5 (low) at Elo 2493 and $0.243 per script leads GPT-5.6 Terra (medium) at Elo 1998 and $0.062 per script by 495 Elo. Their 95% ranges do not overlap.
- Same Level Name, Side by Side. At medium, the one level name both models use, Claude Opus 5.5 has the higher Writing Elo: 2520 against 1998. 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 Configuration Overlapping the Top One. Claude Opus 5.5 (xhigh), at $1.00 per script, is the cheapest configuration whose 95% range overlaps that of Claude Opus 5.5 (max effort), at $2.58 per script: 2727 to 2851 against 2716 to 2845, so the board cannot separate them. Claude Opus 5.5 (max effort) costs about 2.6 times as much per script.
- Cheapest Claude Opus 5.5 Configuration Above GPT-5.6 Terra's Best. The cheapest Claude Opus 5.5 configuration with a higher Writing Elo than GPT-5.6 Terra (ultra), at Elo 2074 and $0.275 per script, is Claude Opus 5.5 (low), at Elo 2493 and $0.243 per script. It costs less than the configuration it beats.
- Lowest to Highest Thinking Level. Claude Opus 5.5 moves +295 Elo from low to max effort, at about 11 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 Opus 5.5 (max effort) scores higher on all nine metrics. Weighted by each metric's share of the Writing Score, Tone & Voice Match does the most to put Claude Opus 5.5 (max effort) ahead, with a 5.9-point lead on that metric. The weight beside each metric is its share of the Writing Score.
Consistency Across Drafts
| Claude Opus 5.5 (max effort) | GPT-5.6 Terra (ultra) | |
|---|---|---|
| Score spread across drafts (±) | 1.44 | 1.38 |
| Lowest script score | 83.6 Script 10 | 79.8 Script 4 |
| Highest script score | 87.3 Script 7 | 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 Opus 5.5 (max effort) minus GPT-5.6 Terra (ultra), and the higher score is in bold.
| Script | Claude Opus 5.5 (max effort) | GPT-5.6 Terra (ultra) | Gap |
|---|---|---|---|
| Script 1 opinion / warning explainer | 84.6 | 81.1 | +3.5 |
| Script 2 news-analysis / skeptical explainer | 85.3 | 82.1 | +3.2 |
| Script 3 personal roadmap / opinion | 86.5 | 82.5 | +4.0 |
| Script 4 short explainer | 87.0 | 79.8 | +7.2 |
| Script 5 news-analysis / opinion explainer | 85.9 | 82.2 | +3.7 |
| Script 6 founder announcement / personal origin story | 86.3 | 83.0 | +3.3 |
| Script 7 personal technical walkthrough / agentic workflow case study | 87.3 | 80.6 | +6.7 |
| Script 8 product release announcement / personal observation | 85.5 | 80.3 | +5.2 |
| Script 9 career guide / hiring analysis | 87.3 | 81.8 | +5.5 |
| Script 10 engineering process walkthrough / presentation adaptation | 83.6 | 80.6 | +3.0 |
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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