# gpt-oss-20b vs Qwen3.5 Plus

> Qwen3.5 Plus is the stronger model overall, scoring 42.3 to 32.1 on the Noometry Index. gpt-oss-20b costs 25× less per token, which makes it the better buy when Qwen3.5 Plus's lead doesn't matter for your workload.

- Canonical page: https://noometry.com/compare/gpt-oss-20b-vs-qwen3-5-plus
- Last updated: 2026-10-10
- Shared benchmarks: 7

## Summary

- They share 7 benchmarks with published results for both. gpt-oss-20b scores higher in 0 categories and Qwen3.5 Plus in 4 categories; 4 gaps are clear of the uncertainty.
- The widest gap is in reasoning, where Qwen3.5 Plus leads 32.0 to 18.8.
- The biggest single-benchmark swing is GPQA Diamond: 60.8% for gpt-oss-20b and 84.8% for Qwen3.5 Plus.
- gpt-oss-20b is cheaper at $0.018 / $0.09 per million input/output tokens, against $0.40 / $2.40 for Qwen3.5 Plus.
- Qwen3.5 Plus accepts more context: 1M tokens versus 131K.
- gpt-oss-20b has downloadable open weights; the other is API-only.

## Snapshot

| | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| Provider | OpenAI | Alibaba (Qwen) |
| Noometry Index | 32.1 | 42.3 |
| Rank | 249 | 103 |
| Context | 131K | 1M |
| Input $/M | $0.018 | $0.40 |
| Output $/M | $0.09 | $2.40 |
| Weights | Open | Proprietary |

## Coding

- gpt-oss-20b: 37.1 (#185)
- Qwen3.5 Plus: —

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| ALE-Bench | 566.05 | 621.92 |
| SciCode | 34.4% | — |
| WeirdML | 40.9% | — |
| LMArena Coding | 1307 | — |

## Agentic & Tool Use

- gpt-oss-20b: 9.2 (#146)
- Qwen3.5 Plus: —

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| Terminal-Bench | 3.4% | — |
| Vending-Bench 2 | — | 0.54 |

## Reasoning

- gpt-oss-20b: 18.8 (#251)
- Qwen3.5 Plus: 32.0 (#67)

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| Chess Puzzles | 4% | 22% |
| DTBench | 68% | 80.5% |
| LMCA | 14.5% | 36.4% |
| Epoch Capabilities Index | 137.81 | 146.79 |
| Kagi LLM Benchmark | 53.2% | — |
| CritPt | 1.4% | — |
| LMArena Hard Prompts | 1274 | — |
| Mystery Game Puzzles | — | 17% |

## Math

- gpt-oss-20b: 37.6 (#93)
- Qwen3.5 Plus: 47.9 (#55)

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 65.3% | 86.7% |
| Omni-MATH | 56.5% | — |
| LMArena Math | 1317 | — |
| FrontierMath (Feb 2025 set) | — | 21% |
| FrontierMath Tier 4 (v1) | — | 2.1% |

## Knowledge

- gpt-oss-20b: 34.6 (#186)
- Qwen3.5 Plus: 46.0 (#78)

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| GPQA Diamond | 60.8% | 84.8% |
| SimpleQA Verified | — | 25.4% |
| MMLU-Pro | 74% | — |
| Vectara Hallucination Rate | — | 10.7% |
| GPQA (HELM) | 59.4% | — |
| LMArena Expert | 1258 | — |

## Multilingual

- gpt-oss-20b: 42.4 (#192)
- Qwen3.5 Plus: —

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| LMArena Non-English | 1269 | — |
| LMArena Chinese | 1311 | — |
| LMArena German | 1249 | — |
| LMArena Japanese | 1245 | — |
| LMArena Korean | 1239 | — |
| LMArena Russian | 1279 | — |
| LMArena Spanish | 1267 | — |

## Instruction Following

- gpt-oss-20b: 62.0 (#235)
- Qwen3.5 Plus: —

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| IFEval | 73.2% | — |
| LMArena Instruction Following | 1236 | — |

## Long Context

- gpt-oss-20b: 37.9 (#203)
- Qwen3.5 Plus: 42.9 (#109)

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| CL-bench | — | 19.8% |
| CL-bench Life | — | 12.4% |
| LMArena Longer Query | 1251 | — |

## Writing & Preference

- gpt-oss-20b: 35.8 (#260)
- Qwen3.5 Plus: —

| Benchmark | gpt-oss-20b | Qwen3.5 Plus |
|---|---|---|
| LMArena Text | 1288 | — |
| LMArena Creative Writing | 1201 | — |
| EQ-Bench Creative Writing | 666 | — |
| WildBench | 73.7% | — |
| LMArena Multi-Turn | 1268 | — |

## FAQ

### Is gpt-oss-20b better than Qwen3.5 Plus?

Qwen3.5 Plus is the stronger model overall, scoring 42.3 to 32.1 on the Noometry Index. gpt-oss-20b costs 25× less per token, which makes it the better buy when Qwen3.5 Plus's lead doesn't matter for your workload.

### Which is cheaper, gpt-oss-20b or Qwen3.5 Plus?

gpt-oss-20b is cheaper. It lists at $0.018 per million input tokens and $0.09 per million output tokens; Qwen3.5 Plus lists at $0.40 and $2.40.

### Which has the bigger context window?

Qwen3.5 Plus does, with 1M tokens against 131K.

### How many benchmarks do gpt-oss-20b and Qwen3.5 Plus share?

7 benchmarks have published results for both models. gpt-oss-20b has 34 scored results on Noometry and Qwen3.5 Plus has 15.