Stable Diffusion 3.5 Medium vs Flux 1.1 Pro Ultra: Which AI Model Should You Choose?
Pricing, context windows, latency, capabilities, and a one-line code switch — everything you need to pick the right model.
Stable Diffusion 3.5 Medium and Flux 1.1 Pro Ultra are closely matched on pricing and context. The right choice depends on your specific workload — see the table below for the full breakdown.
Side-by-side specs
| Spec | Stable Diffusion 3.5 Medium | Flux 1.1 Pro Ultra |
|---|---|---|
| Provider | Replicate | Replicate |
| Category | Image Generation | Image Generation |
| Input cost / 1M tokens | n/a | n/a |
| Output cost / 1M tokens | n/a | n/a |
| Context window | — | — |
| Max output tokens | — | — |
| Avg. latency | — | 15.0s |
| Featured | — | Yes |
| New | Yes | — |
| Capabilities | text | jpg png |
Pricing example
A typical chat workload of 100,000 input tokens plus 50,000 output tokens.
100K in × n/a + 50K out × n/a
100K in × n/a + 50K out × n/a
Switch in one line
Both models live behind Railwail's OpenAI-compatible endpoint. Replace the model string and you are done.
import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.RAILWAIL_API_KEY,
baseURL: "https://railwail.com/v1",
});
// Before — using Stable Diffusion 3.5 Medium
let r = await client.chat.completions.create({
model: "stability-ai/stable-diffusion-3.5-medium",
messages: [{ role: "user", content: "Hello" }],
});
// After — switched to Flux 1.1 Pro Ultra
r = await client.chat.completions.create({
model: "black-forest-labs/flux-1.1-pro-ultra",
messages: [{ role: "user", content: "Hello" }],
});from openai import OpenAI
client = OpenAI(
api_key=os.environ["RAILWAIL_API_KEY"],
base_url="https://railwail.com/v1",
)
# Before — using Stable Diffusion 3.5 Medium
r = client.chat.completions.create(
model="stability-ai/stable-diffusion-3.5-medium",
messages=[{"role": "user", "content": "Hello"}],
)
# After — switched to Flux 1.1 Pro Ultra
r = client.chat.completions.create(
model="black-forest-labs/flux-1.1-pro-ultra",
messages=[{"role": "user", "content": "Hello"}],
)# Before — using Stable Diffusion 3.5 Medium
curl https://railwail.com/v1/chat/completions \
-H "Authorization: Bearer $RAILWAIL_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "stability-ai/stable-diffusion-3.5-medium",
"messages": [{"role": "user", "content": "Hello"}]
}'
# After — switched to Flux 1.1 Pro Ultra
curl https://railwail.com/v1/chat/completions \
-H "Authorization: Bearer $RAILWAIL_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "black-forest-labs/flux-1.1-pro-ultra",
"messages": [{"role": "user", "content": "Hello"}]
}'Which one wins for...
Quick verdicts derived from public specs. Always validate on your own workload.
Higher coding category match or larger context wins.
Bigger context window helps maintain long-form coherence.
The larger context window is the deciding factor.
Multimodal/vision support is required for image inputs.
Lower average latency wins for interactive UX.
The model with the lower input-token price wins.
Frequently asked questions
Try Stable Diffusion 3.5 Medium and Flux 1.1 Pro Ultra side by side
One API key, one endpoint, both models. Start free — no credit card required.