Gemini 3.5 vs GPT-5.5 Instant
Pricing, benchmarks, and use case comparison
Quick take
- •Gemini 3.5 is meaningfully stronger at cost efficiency (85 vs 70 on our capability index).
- •Gemini 3.5 is 70% cheaper on input tokens, which compounds fast on high-volume or agentic workloads.
- •GPT-5.5 Instant has a 1050000 context window vs 1,048,576 tokens (Gemini 3.5 Flash; Pro variant not yet released) - better for whole-repo or long-document work.
Specs comparison
| Gemini 3.5 | GPT-5.5 Instant | |
|---|---|---|
| Provider | Google DeepMind | OpenAI |
| Type | Closed source | Closed source |
| Context window | 1,048,576 tokens (Gemini 3.5 Flash; Pro variant not yet released) | ✓1050000 |
| Input / 1M tokens | ✓$1.50 | 5.00 |
| Output / 1M tokens | $9.00 | 30.00 |
| Release date | 2026-05 | 2026-05 |
Benchmarks
| Benchmark | Gemini 3.5 | GPT-5.5 Instant |
|---|---|---|
| Terminal-Bench 2.1 (coding) | 76.2% | - |
| MCP Atlas (tool use) | 83.6% | - |
| CharXiv Reasoning (multimodal) | 84.2% | - |
| AIME 2025 | - | 81.2 |
| Terminal-Bench 2.0 | - | 82.7 |
| FrontierMath Tier 1–3 | - | 51.7 |
Scores sourced from official provider release posts and independent benchmark aggregators.
Which should you choose?
Choose Gemini 3.5 if...
- →You need frontier agent/coding performance without frontier prices
- →Building autonomous agents that make many tool calls
- →High-throughput production workloads that were previously too costly on a Pro model
- →You want a strong default multimodal model with a 1M-token context window
Choose GPT-5.5 Instant if...
- →Interactive chat and everyday assistant tasks where responsiveness matters most
- →High-volume, latency-sensitive workloads that do not need deep reasoning
- →General questions, drafting, and summarization at speed