Claude Opus 5 (max) vs Grok 4.5
Should you write with Claude Opus 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 Opus 5 (max) leads overall, 89.4 to 81.9. Heads-up: Claude Opus 5 (max) shares its model line with one of the three judges. The panel spans three model families, so no model here is scored by its own family alone (how the panel works).
The verdict
Grok 4.5 is fast, under a minute per script, and cheap at about six cents. That's about all it has on Claude Opus 5 (max effort) here, which sits at #8 while Grok 4.5 sits at #76. The biggest single gap is length: about fifteen points behind on Length Adherence, so its scripts miss the target by a lot. Flow trails too, about nine points on Continuity & Emotion, a metric the rubric weights more heavily than length. Grok doesn't beat Opus on a single metric. And when the better option still costs under thirty cents per script, I'd rather pay for scripts I don't have to restructure.
Pick Claude Opus 5 (max effort) for scripts that hold together and hit their length, still at a low price.
Pick Grok 4.5 for near-instant, cheap drafts when length and flow don't matter.
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 Opus 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, Tone & Voice Match does the most to put Claude Opus 5 (max) ahead: it leads there by 7.3 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 Opus 5 (max) costs about 4.7x as much per script as Grok 4.5.
| Claude Opus 5 (max) | Grok 4.5 | |
|---|---|---|
| Overall / 100 | 89.4 | 81.9 |
| Writing Elo | 2354 | 1618 |
| Score spread across drafts (± overall std) | 1.190 | 2.950 |
| Cost per script (USD) | 0.293 | 0.063 |
| Avg time per script (min) | 2.2 | 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 Opus 5 (max) · Grok 4.5. The whole scoring pipeline is on the methodology page.
← All comparisons