GPT Image 1.5vs.Stable Diffusion 3 Medium

Which one is better?

In our own test, GPT Image 1.5 leads. Stable Diffusion 3 Medium has no arena rating yet. Stable Diffusion 3 Medium has no API price.

Test images

Same task, the first image of each. The task with the biggest difference is preselected.

GPT Image 1.5: Character and detail, first image from the fixed test run — GPT Image 1.589 out of 100

Stable Diffusion 3 Medium: Character and detail, first image from the fixed test run — Stable Diffusion 3 Medium46 out of 100

Result for “Character and detail”:GPT Image 1.5 ahead

Prompt given to both modelsCreate a square cinematic full-body portrait of a fictional bicycle courier waiting under a transparent umbrella at a rainy tram stop in Hamburg at blue hour. She wears a mustard raincoat, navy trousers, red sneakers, a silver helmet, and carries a teal messenger bag. Keep both hands visible, render the bicycle correctly, use realistic wet-street reflections, and include no readable brand names.

What the rating looks at: Anatomy, clothing, and spatial consistency.

“Ahead”: better in all three rating rounds. “Slightly ahead”: a higher value, but not in every round.

Test protocol of the images

Each test attempt uses the same archived prompt and one request. The first output of that attempt counts. Repeats after technical test failures are disclosed for the affected images. Files are normalized to 1,024 × 1,024 pixels without cropping. Provider resolution, randomness, quality tier and prompt processing can still differ. The images are a practical visual test, not a reconstruction of the arena configuration.

Character and detail

GPT Image 1.5: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 12:17 PM. Source

Stable Diffusion 3 Medium: fal, requested 1024x1024, n=1, seed=provider random, prompt expansion disabled, estimated cost $0.035000, generated Nov 2, 2026, 3:25 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: 985a75b38642a9f0e5e0c0e0c67f1b7f67780d42bd2168fa24e9a7a7a94b0da6

GPT Image 1.5 image SHA 256: 0dff52ccd39400ac66ac8870c9ea937512ff1474688e70118688f420c38c2296

Stable Diffusion 3 Medium image SHA 256: 23f00c74639e751fd6130d5f0e06539379c3a631d3f3cfde39c43e31973f5ef4

Infographic

GPT Image 1.5: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 12:17 PM. Source

Stable Diffusion 3 Medium: fal, requested 1024x1024, n=1, seed=provider random, prompt expansion disabled, estimated cost $0.035000, generated Nov 2, 2026, 3:26 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: ed65cb4e6a51e2336f8b149ad4cbb16e020f07d527ad94362e719d2dcf91d94f

GPT Image 1.5 image SHA 256: 1c9ff59c32621c8b48b002dacb0ae66487262280c7c0a5b3d6456c81b248ebe9

Stable Diffusion 3 Medium image SHA 256: d3247357eaa74b5b9157558cec7ffc4942c0a0fe09b5b7d661289d63c0359fbb

Product photography

GPT Image 1.5: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 12:16 PM. Source

Stable Diffusion 3 Medium: fal, requested 1024x1024, n=1, seed=provider random, prompt expansion disabled, estimated cost $0.035000, generated Nov 2, 2026, 3:25 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: c67fd71e91304458a2feef5c91efa8677260fab0c0099a29a2c52cb579f5b2f3

GPT Image 1.5 image SHA 256: 67cfa2f324447027ceb5f82e9446d40a1395b46ce425890a74606b4d97731cf6

Stable Diffusion 3 Medium image SHA 256: 7214318e9962af2466367b9ac75231f5b794a5db5a0b6d11d6e6f6a378cb28b6

Typography and layout

GPT Image 1.5: together, 1024x1024, n=1, seed=provider random, provider default steps, generated Aug 14, 2026, 1:59 PM. Source

Stable Diffusion 3 Medium: fal, requested 1024x1024, n=1, seed=provider random, prompt expansion disabled, estimated cost $0.035000, generated Nov 2, 2026, 3:25 PM. Source

Protocol gradually-image-comparison-v1. Prompt SHA 256: 2e012c3d14ee5dd02203a94f394ca80a5038cdebd6032b25a8b8a221f2255419

GPT Image 1.5 image SHA 256: 6a4cec86850fd371b65274198e2bf630b3cf36a096f9fb953d4bfe17c3222ebe

Stable Diffusion 3 Medium image SHA 256: 9dd323604b3bfc1742a51a2ca225f9c0f8dfbe79f5fa68e6024015316c596a54

The numbers at a glance

Arena ratingfrom votes by users · higher is better

1,236

GPT Image 1.5

Rank 13 of 21

n/a

Stable Diffusion 3 Medium

not in the arena

GraduallyBenchour own rating, 0 to 100 · higher is better

GPT Image 1.5

Rank 29 of 108

Stable Diffusion 3 Medium

Rank 78 of 108

Price per imagedollars through the API · lower is better

$0.13

GPT Image 1.5

expensive

n/a

Stable Diffusion 3 Medium

no API price

Ranks among the 21 image models with an arena rating and the 108 with a GraduallyBench run; prices compared with 28 models with an API price.

GPT Image 1.5

Subscription: No OpenAI subscription includes this model. Through other providers from ≈ €6.36 a month (ElevenLabs Starter, with limited credits). 42 plans in Germany.
Via API: $0.13 per image, 100 images $13.30.

Stable Diffusion 3 Medium

Subscription: n/a No plan in Germany names exactly this model.
Via API: No API price known. Access: API, local.
License: Open weights.

Subscriptions only count plans that name exactly this model. Subscription prices include VAT, API prices are in dollars.

Arena rating (LMArena) from Nov 6, 2026 · GraduallyBench from Nov 3, 2026 · API prices from Nov 6, 2026 · Subscription database from Sep 29, 2026 (38 days old)

All data side by side

The better value is bold. For ratings only when the gap is clear.

Kennzahl	GPT Image 1.5	Stable Diffusion 3 Medium
Ratings
Arena ratingfrom votes by users, higher is better	1,236	n/a
Arena rank	Rank 13 of 21	n/a
Arena votesmore votes, a safer rating	173,798	n/a
GraduallyBenchour own rating, 0 to 100	68	34
GraduallyBench by task
Typography and layoutLegible text, hierarchy, and composition	60	31
Product photographyMaterials, reflections, and fine details	52	26
Character and detailAnatomy, clothing, and spatial consistency	89	46
InfographicNumbers, labels, and visual organization	72	34
API price
Per imagelower is better	$0.13	n/a
100 images	$13.30	n/a
Profile
Released	December 2025	Jun 12, 2024
Weightsopen means: runs locally	proprietary	open
Lifecycle	Marked as deprecated by OpenAI; removed from the API on December 1, 2026	no notice
Access	API, Web app	API, local
Parameters	not published	2 billion
Largest output	1,536 × 1,024 pixels	not consistently published
Plans in Germanynaming exactly this model	42	n/a

API prices for one image at 1,024 × 1,024 pixels according to Artificial Analysis.

Sources: GPT Image 1.5 model source, status source (verified Aug 15, 2026) · Stable Diffusion 3 Medium model source (verified Nov 1, 2026)

Arena ratings by category

From blind votes on LMArena. “Ahead” means the lead is clear.

No shared arena score in the stored snapshot

The stored benchmark database contains no measurement for GPT Image 1.5 and Stable Diffusion 3 Medium from the same arena and category. Older model versions are not used as substitutes.

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