Claude Fable 5 (max) vs Grok 4.5
Should you write with Claude Fable 5 (max) or Grok 4.5? On this page the only thing that changes is the model. Both wrote their own version of the scripts behind 10 of my What's AI videos, five drafts per script, and three judges from three model families scored every draft blind, with my finished script as the reference. Claude Fable 5 (max) leads overall, 89.7 to 81.9.
The verdict
Grok 4.5 is built for speed, and its scores show it. Its biggest gap against Claude Fable 5 (max effort + 4.8 fallback) is length: about twenty points behind on Length Adherence, so its scripts miss their target. It's also about nine points behind on Continuity & Emotion, which carries more weight in the rubric than length does. Grok doesn't beat Fable anywhere in this pairing, and the board has them at #76 and #5. Its case is speed and price: under a minute per script, about six cents against two and a half dollars. Fine for quick internal notes. For a script you'll record, I wouldn't bother.
Pick Claude Fable 5 (max effort + 4.8 fallback) for any script that has to land at the right length and hold together.
Pick Grok 4.5 for very fast, low-cost drafts where length and flow don't matter much.
How to read these numbers
Overall vs Elo. Overall is the weighted rubric score. Elo compares each model's five-draft average with every other model's, script by script, and counts gaps inside run-to-run noise as draws, so it rewards winning often and can disagree with overall. My own scripts score 90.9 on the same rubric, not a literal 100. Right now 2 of 167 ranked configurations reach it. A model above that line writes at that level on this rubric. That's not the same as beating my script line for line.
Reading the Elo intervals. Each 95% range comes from resampling every model's recorded run scores on each task and re-ranking. Comparing these separate ranges does not test the Elo gap between two models: far apart is strong evidence, and overlap isn't a tie. The tasks stay fixed, so the ranges say nothing about new tasks (the long version).
Metric by metric: where the gap comes from
Blue is Claude Fable 5 (max), orange is Grok 4.5, and the solid bar takes the metric. The weight under each name is how much it counts toward the overall. Weighted by how much each metric counts, Length Adherence does the most to put Claude Fable 5 (max) ahead: it leads there by 20.0 points. If you care about one thing, say voice or length, go straight to that row.
Cost, speed, and consistency
Quality is half the decision. The other half is what each script costs you, how long you wait, and how often you get a bad draft. The lead has a price: Claude Fable 5 (max) costs about 40x as much per script as Grok 4.5.
| Claude Fable 5 (max) | Grok 4.5 | |
|---|---|---|
| Overall / 100 | 89.7 | 81.9 |
| Writing Elo | 2392 | 1618 |
| Score spread across drafts (± overall std) | 1.360 | 2.950 |
| Cost per script (USD) | 2.522 | 0.063 |
| Avg time per script (min) | 9.1 | 0.9 |
| Open weights | No | No |
Green wins the row, and for spread, cost and time, lower wins. Cost is one script at recorded list prices, uncached and without judging, so your real bill will differ. Spread is how much the overall score moves across a model's drafts, and time is the average time to get one accepted script, retries included.
Want the script-by-script detail? Full scorecards: Claude Fable 5 (max) · Grok 4.5. The whole scoring pipeline is on the methodology page.
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