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Opus 5 or Gemini 3.1 Pro: a comparison with incomplete data coverage on one side
Gemini 3.1 Pro carries a lower operating cost, $2 and $12 against $5 and $25, but only below the 200,000-token threshold; above that point the rate shifts to $4 and $18. Opus 5 holds one fixed rate across its entire one-million-token window, and Google publishes no context window at all for this Gemini model.
Specifications where both sides have a verified figure on record
| Claude Opus 5 | Gemini 3.1 Pro | |
|---|---|---|
| API model ID | claude-opus-5 | gemini-3.1-pro-preview |
| Input price | $5 per million tokens | $2 per million tokens |
| Output price | $25 per million tokens | $12 per million tokens |
A row where one side lacks a verified figure is dropped from the table entirely, because a half-empty row biases the reader toward the filled side.
Why the specification table above has three rows
Because most of the parameters needed for comparison are unpublished on one side. The Gemini API model page carries no context window, no output ceiling and no knowledge cutoff for gemini-3.1-pro-preview. Opus 5 publishes all three parameters. A row with one empty cell is not built into the table, because readers interpret a half-empty row in favor of the filled side.
Tiered pricing, and the point where "half the price" collapses
The Gemini figures in the table above belong to the tier below 200,000 tokens. From 200,000 tokens up, input becomes $4 and output $18. So exactly at the point where large window capacity earns its return, the price gap closes from "less than half" to "about three quarters". Opus 5 has no such step in its pricing structure; its $5 and $25 rate holds constant to the end of the window.
One system gets ranked, the other does not
In our coding ranking table, Opus 5 stands first with source backing in all six columns. Gemini 3.1 Pro receives no rank at all, because 85 of the 100 weight units across our criteria are empty for it: the web-dev leaderboard row, the context window and the tooling maturity score. Its only complete column is price. Do not read this as a judgment on model quality; it is the state of published data coverage, and a model still in preview is entitled to incomplete specifications.
This is the right pick if Claude Opus 5
- You want to know exactly what you are purchasing: window, output ceiling and knowledge cutoff are all published.
- Your workload is code. Opus 5 is first in our table and Gemini 3.1 Pro receives no rank at all.
- You send long inputs and do not want the price to step up mid-processing.
This is the right pick if Gemini 3.1 Pro
- Cost per token is the deciding parameter and your prompts stay under 200,000 tokens.
- The rest of your infrastructure runs on Google and you want to keep the same account.
- You are comfortable with a model still in preview whose full specification is unpublished.
Frequently raised questions, with documented answers
Which system carries the lower operating cost
Gemini 3.1 Pro, conditionally. Below 200,000 tokens it charges $2 and $12 against $5 and $25 for Opus 5. From 200,000 tokens up the rate becomes $4 and $18 and the gap narrows sharply.
Why is Gemini 3.1 Pro unranked in your coding table
Because more than half the criteria weight has no source backing it: the web-dev leaderboard row is unrecorded for it, and Google publishes neither a context window nor anything scorable for tooling maturity. Our rule leaves a candidate unranked when more than half of its specification is empty.