Model Comparison

GPT-5.5 Pro vs U2Which is better in 2026?

Comparing GPT-5.5 Pro and U2 across benchmarks, pricing, and capabilities.

Verdict: GPT-5.5 Pro vs U2 — which is better?

GPT-5.5 Pro (by OpenAI) and U2 (by Unisound) are two of the AI models people compare most. Here is how they stack up on benchmarks, price and capabilities, and which one to pick in 2026.

On price, U2 is roughly 360.0x cheaper per token on a blended 3:1 input/output basis, which adds up quickly at production volume.

Choose GPT-5.5 Pro if…

  • you want predictable pricing at $30.00/M input and $180.00/M output

Choose U2 if…

  • cost matters — it's about 360.0x cheaper per token
  • you want the most recent training data — it shipped Jun 2026

Performance Benchmarks

Comparative analysis across standard metrics

No common benchmarks found

GPT-5.5 Pro and U2don't have any common benchmark datasets to compare. They may have been evaluated on different testing suites.

Arena Performance

Human preference votes

Pricing Analysis

Price comparison per million tokens

U2 costs less

For input processing, GPT-5.5 Pro ($30.00/1M tokens) is 200.0x more expensive than U2 ($0.15/1M tokens).

For output processing, GPT-5.5 Pro ($180.00/1M tokens) is 600.0x more expensive than U2 ($0.30/1M tokens).

In conclusion, GPT-5.5 Pro is more expensive than U2.*

* Using a 3:1 ratio of input to output tokens

Lowest available price from all providers
Fri Jul 17 2026 • llm-stats.com
OpenAI
GPT-5.5 Pro
Input tokens$30.00
Output tokens$180.00
Best providerOpenAI
Unisound
U2
Input tokens$0.15
Output tokens$0.30
Best providerUnisound
Notice missing or incorrect data?Start an Issue→

Context Window

Maximum input and output token capacity

Only GPT-5.5 Pro specifies input context (1,050,000 tokens). Only GPT-5.5 Pro specifies output context (128,000 tokens).

OpenAI
GPT-5.5 Pro
Input1,050,000 tokens
Output128,000 tokens
Unisound
U2
Input- tokens
Output- tokens
Fri Jul 17 2026 • llm-stats.com

Input Capabilities

Supported data types and modalities

GPT-5.5 Pro supports multimodal inputs, whereas U2 does not.

GPT-5.5 Pro can handle both text and other forms of data like images, making it suitable for multimodal applications.

GPT-5.5 Pro

Text
Images
Audio
Video

U2

Text
Images
Audio
Video

License

Usage and distribution terms

Both models are licensed under proprietary licenses.

Both models have usage restrictions defined by their respective organizations.

GPT-5.5 Pro

Proprietary

Closed source

U2

Proprietary

Closed source

Release Timeline

When each model was launched

GPT-5.5 Pro was released on 2026-04-23, while U2 was released on 2026-06-05.

U2 is 1 month newer than GPT-5.5 Pro.

GPT-5.5 Pro

Apr 23, 2026

2 months ago

U2

Jun 5, 2026

1 months ago

1mo newer

Knowledge Cutoff

When training data ends

GPT-5.5 Pro has a knowledge cutoff of 2025-12-01, while U2 has a cutoff of 2026-01-31.

U2 has more recent training data (up to 2026-01-31), making it potentially better informed about events through that date compared to GPT-5.5 Pro (2025-12-01).

GPT-5.5 Pro

Dec 2025

U2

Jan 2026

1 mo newer

Provider Availability

GPT-5.5 Pro is available from OpenAI. U2 is available from Unisound.

GPT-5.5 Pro

openai logo
OpenAI
Input Price:Input: $30.00/1MOutput Price:Output: $180.00/1M

U2

unisound logo
Unisound
Input Price:Input: $0.15/1MOutput Price:Output: $0.30/1M
* Prices shown are per million tokens

Outputs Comparison

Notice missing or incorrect data?Start an Issue discussion→

Key Takeaways

OpenAI
Larger context window (1,050,000 tokens)
Supports multimodal inputs
Unisound
Less expensive input tokens
Less expensive output tokens

Detailed Comparison

Interactive Arena

Judge for yourself.

Run your own prompts against GPT-5.5 Pro and U2 side-by-side, then vote on the output you prefer.

GPT-5.5 Pro
✓ Preferred
U2
Open in Playground
AI Model Comparison Table
Feature
OpenAI
GPT-5.5 Pro
Unisound
U2

FAQ

Common questions about GPT-5.5 Pro vs U2.

Which is better, GPT-5.5 Pro or U2?

GPT-5.5 Pro (OpenAI) and U2 (Unisound) each have strengths in different areas. Compare their benchmark scores, pricing, context windows, and capabilities above to determine which fits your needs.

How does GPT-5.5 Pro compare to U2 in benchmarks?

GPT-5.5 Pro scores BrowseComp: 90.1%, GDPval-MM: 82.3%, Humanity's Last Exam: 57.2%, FrontierMath: 39.6%, GeneBench: 33.2%.

Is GPT-5.5 Pro cheaper than U2?

U2 is 200.0x cheaper for input tokens. GPT-5.5 Pro costs $30.00/M input and $180.00/M output via openai. U2 costs $0.15/M input and $0.30/M output via unisound.

What are the context window sizes for GPT-5.5 Pro and U2?

GPT-5.5 Pro supports 1.1M tokens and U2 supports an unknown number of tokens. A larger context window lets you process longer documents, conversations, or codebases in a single request.

What are the main differences between GPT-5.5 Pro and U2?

Key differences include input pricing ($30.00 vs $0.15/M), multimodal support (yes vs no). See the full comparison above for benchmark-by-benchmark results.

Who makes GPT-5.5 Pro and U2?

GPT-5.5 Pro is developed by OpenAI and U2 is developed by Unisound.

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