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Gemini 1.5 Pro (vision) vs Gemini 3.1 Pro: 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.

Google
Multimodal
vs
Google
Multimodal
Verdict

Gemini 1.5 Pro (vision) and Gemini 3.1 Pro 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

SpecGemini 1.5 Pro (vision)Gemini 3.1 Pro
ProviderGoogleGoogle
CategoryMultimodalMultimodal
Input cost / 1M tokens€0.0010€0.0020
Output cost / 1M tokens€0.0050€0.012
Context window2.1M tokens2.0M tokens
Max output tokens8,19265,536
Avg. latency——
FeaturedYesYes
New—Yes
Capabilities
text
image
audio
video
text
image
audio
video

Pricing example

A typical chat workload of 100,000 input tokens plus 50,000 output tokens.

Gemini 1.5 Pro (vision)
€0.0003

100K in × €0.0010 + 50K out × €0.0050

Gemini 3.1 Pro
€0.0008

100K in × €0.0020 + 50K out × €0.012

For this workload, Gemini 1.5 Pro (vision) is cheaper than Gemini 3.1 Pro by €0.0005 per request.

Switch in one line

Both models live behind Railwail's OpenAI-compatible endpoint. Replace the model string and you are done.

JavaScript / TypeScript
import OpenAI from "openai";

const client = new OpenAI({
  apiKey: process.env.RAILWAIL_API_KEY,
  baseURL: "https://railwail.com/v1",
});

// Before — using Gemini 1.5 Pro (vision)
let r = await client.chat.completions.create({
  model: "gemini-1.5-pro",
  messages: [{ role: "user", content: "Hello" }],
});

// After — switched to Gemini 3.1 Pro
r = await client.chat.completions.create({
  model: "gemini-3.1-pro",
  messages: [{ role: "user", content: "Hello" }],
});
Python
from openai import OpenAI

client = OpenAI(
    api_key=os.environ["RAILWAIL_API_KEY"],
    base_url="https://railwail.com/v1",
)

# Before — using Gemini 1.5 Pro (vision)
r = client.chat.completions.create(
    model="gemini-1.5-pro",
    messages=[{"role": "user", "content": "Hello"}],
)

# After — switched to Gemini 3.1 Pro
r = client.chat.completions.create(
    model="gemini-3.1-pro",
    messages=[{"role": "user", "content": "Hello"}],
)
cURL
# Before — using Gemini 1.5 Pro (vision)
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-1.5-pro",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

# After — switched to Gemini 3.1 Pro
curl https://railwail.com/v1/chat/completions \
  -H "Authorization: Bearer $RAILWAIL_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gemini-3.1-pro",
    "messages": [{"role": "user", "content": "Hello"}]
  }'

Which one wins for...

Quick verdicts derived from public specs. Always validate on your own workload.

Coding
Gemini 1.5 Pro (vision)

Higher coding category match or larger context wins.

Writing
Gemini 1.5 Pro (vision)

Bigger context window helps maintain long-form coherence.

Long documents
Gemini 1.5 Pro (vision)

The larger context window is the deciding factor.

Vision
Tie

Multimodal/vision support is required for image inputs.

Real-time chat
Tie

Lower average latency wins for interactive UX.

Cost-sensitive
Gemini 1.5 Pro (vision)

The model with the lower input-token price wins.

Frequently asked questions

Which is cheaper, Gemini 1.5 Pro (vision) or Gemini 3.1 Pro?
Gemini 1.5 Pro (vision) is cheaper. On a 100K input + 50K output example, Gemini 1.5 Pro (vision) costs about €0.0003 versus €0.0008 for Gemini 3.1 Pro — a saving of €0.0005.
Which has more context, Gemini 1.5 Pro (vision) or Gemini 3.1 Pro?
Gemini 1.5 Pro (vision) has the larger context window at 2.1M tokens, compared to 2.0M tokens for Gemini 3.1 Pro.
Is Gemini 1.5 Pro (vision) better than Gemini 3.1 Pro for coding?
For coding-heavy workloads we lean toward Gemini 1.5 Pro (vision) on this comparison — it scores higher on the relevant heuristics (category, tags, or context window). Both models are usable for code via Railwail's OpenAI-compatible endpoint, so the safest path is to A/B test on your own prompts.
Can I use both Gemini 1.5 Pro (vision) and Gemini 3.1 Pro via Railwail?
Yes. Both Gemini 1.5 Pro (vision) and Gemini 3.1 Pro are accessible through a single Railwail API key and the OpenAI-compatible /v1/chat/completions endpoint. You only change the "model" parameter to switch between them — no SDK swap, no separate billing.
How do I switch from Gemini 1.5 Pro (vision) to Gemini 3.1 Pro?
Replace the model identifier "gemini-1.5-pro" with "gemini-3.1-pro" in your request payload. Everything else — API key, base URL, request shape — stays the same. See the code example on this page for the exact one-line change.

Try Gemini 1.5 Pro (vision) and Gemini 3.1 Pro side by side

One API key, one endpoint, both models. Start free — no credit card required.

Get Started FreeView Gemini 1.5 Pro (vision)View Gemini 3.1 Pro