# Flux 1.1 Pro Ultra vs Stable Diffusion 3.5: which open-ish model wins?

**Source:** https://promtable.com/compare/flux-vs-stable-diffusion-3

> Flux 1.1 Pro Ultra is the higher-fidelity, prompt-adherence king but partly closed; SD 3.5 Large is genuinely open and the ComfyUI ecosystem winner. Pick Flux for quality, SD for control.

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Flux 1.1 Pro Ultra is the higher-fidelity, prompt-adherence king but partly closed; SD 3.5 Large is genuinely open and the ComfyUI ecosystem winner. Pick Flux for quality, SD for control.

## At a glance

| Dimension | Flux 1.1 Pro Ultra | Stable Diffusion 3.5 Large |
|---|---|---|
| Output quality (default) | **State of the art** ✓ | Strong but a notch below |
| Prompt adherence | **Excellent** ✓ | Very good |
| Text in images | **Excellent** ✓ | Decent, lags Flux |
| Open weights | Only Flux 1 dev (older) | **Yes — SD 3.5 Large fully open** ✓ |
| ControlNet / IP-Adapter ecosystem | Newer, fewer extensions | **Largest in the industry** ✓ |
| Fine-tuning / LoRA | Supported on dev | **Mature ecosystem** ✓ |
| Price (API) | ~$0.04/image (Pro Ultra) | **Open weights — compute only** ✓ |
| Speed | **5-15 s on Pro Ultra** ✓ | 12-30 s on a 24 GB GPU |

## Verdict

If you need the absolute best one-shot quality on a brief, Flux 1.1 Pro Ultra wins; the gap on prompt adherence and text rendering is real. If you need to fine-tune on a brand, deploy on your own infra, or run ControlNet + IP-Adapter pipelines, Stable Diffusion 3.5 Large is still the platform — the ComfyUI ecosystem around it is years ahead of anything Flux has.

## When to pick which

- **Flux 1.1 Pro Ultra** — Top-quality hero shots, ads, on-image typography, fastest path to a clean result.
- **Stable Diffusion 3.5 Large** — Self-hosting, custom LoRA on a character or brand, ControlNet workflows, infinite iteration.

## FAQ

### Is Flux better than Stable Diffusion 3.5?

On default output quality and prompt adherence, yes. On ecosystem, customisation, and self-hosting, Stable Diffusion 3.5 Large is still ahead.

### Can I run Flux locally?

Yes — Flux 1 dev (older, smaller) runs on a 24 GB GPU with quantization. Flux 1.1 Pro Ultra is API-only.

### Which is cheaper for high volume?

Stable Diffusion 3.5 Large on your own hardware is cheaper at scale; below ~5,000 images/month Flux 1.1 Pro Ultra wins on total cost.

## Related

- [/compare/midjourney-vs-flux](https://promtable.com/compare/midjourney-vs-flux)
- [/glossary/diffusion-model](https://promtable.com/glossary/diffusion-model)
- [/glossary/cfg-scale](https://promtable.com/glossary/cfg-scale)

*Last updated: 2026-06-01*
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Original page: https://promtable.com/compare/flux-vs-stable-diffusion-3
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