ResearchLLM Verifications Leaderboard

Data as of · 78 models, 80 questions · reviewed by Suhas Bhairav · methodology

Head to head · tested 27 Oct 2026

GPT-5.3-Codex vs gpt-oss-20b: accuracy, speed and price

GPT-5.3-Codex is more accurate; gpt-oss-20b is cheaper.

OpenAIGPT-5.3-Codex82.5% score · #3$0.01 per question95 tok/sOpenAIgpt-oss-20b51.2% score · #46$0.000066 per question103 tok/s

Verdict

Built from the measurements below

  • GPT-5.3-Codex is more accurate: 82.5% against 51.2% on the same 80 questions, a 31.3-point gap that is statistically significant.
  • gpt-oss-20b is 157× cheaper per question as billed ($0.000066 vs $0.01), reasoning tokens included.
  • Output speed is similar (95 vs 103 tokens per second).
  • gpt-oss-20b starts answering sooner: 0.7 s to the first token, against 1.4 s for GPT-5.3-Codex.
  • GPT-5.3-Codex accepts more context: 400k tokens against 131k.

Which should you choose?

Choose GPT-5.3-Codex for the most accurate answers of the two and a 400k-token context window. Choose gpt-oss-20b for the lower cost per correct answer ($0.00013 against $0.013), a quicker first token, open weights you can run yourself and more hosts to choose from on OpenRouter (10 against 2). The widest subject gap is in engineering: GPT-5.3-Codex answered 11 of 15 correctly, gpt-oss-20b 4 of 15. With so few questions per subject, treat this as a lead to test on your own prompts, not a result.

Accuracy gap +31.3 points (z = 4.20). A winner is called only when z is at least 1.96, the usual 95% threshold. Speed, latency and price need a 10% margin.

Head to head

Same questions, same prompt, same API

MeasureGPT-5.3-Codexgpt-oss-20bEdge
Verification scoreHigher is better82.5%51.2%GPT-5.3-Codex
Cost per questionLower is better$0.01$0.000066gpt-oss-20b
Output speedHigher is better95103Similar
Time to first tokenLower is better1.4 s0.7 sgpt-oss-20b
End-to-end response timeLower is better5.2 s4.0 sgpt-oss-20b
Tokens per questionLower is better699472gpt-oss-20b
Context windowHigher is better400k131kGPT-5.3-Codex

Side by side

Bars are scaled to the larger of the two values. The winner on each measure is marked in bold.

Every measure

GPT-5.3-Codex first, gpt-oss-20b second

Verification scorehigher is better
GPT-5.3-Codex82.5%
gpt-oss-20b51.2%
Cost per questionlower is better
GPT-5.3-Codex$0.01
gpt-oss-20b$0.000066
Output speedhigher is better
GPT-5.3-Codex95
gpt-oss-20b103
Time to first tokenlower is better
GPT-5.3-Codex1.4 s
gpt-oss-20b0.7 s
End-to-end response timelower is better
GPT-5.3-Codex5.2 s
gpt-oss-20b4.0 s
Tokens per questionlower is better
GPT-5.3-Codex699
gpt-oss-20b472
Context windowhigher is better
GPT-5.3-Codex400k
gpt-oss-20b131k

Score vs. cost per question

Both models in color, every other model in grey

Most attractive quadrant0255075100$0.00001$0.0001$0.001$0.01$0.10Cost per question (USD, log) →Verification score (%) →Qwen3.8 2.4T A95BCommand AReka Flash 3Gemma 4 26B A4BGemma 4 31BQwen3.5 397B A17BHermes 4 405BMuse WonderGrok 4.7o3gpt-oss-20bMinistral 3 3B 2512Nova Micro 1.0Phi 4Granite 4.2 8BHy3GLM 5.3 FlashSolar Pro 4Trinity Large ThinkingMiniMax M3Mistral Large 4Claude Opus 5.5GPT-6.1 SolGemini 4 ArgonGPT-5.4GPT-6 Lunagpt-oss-120bLlama 4 Maverick

Specifications and pricing

From OpenRouter's catalogue, plus the leaderboard's test dates

SpecificationGPT-5.3-Codexgpt-oss-20b
CreatorOpenAIOpenAI
Released24 Feb 20265 Aug 2025
Weights—Open weights
ReasoningYesYes
Inputtext, image, filetext
Outputtexttext
Context window400k tokens131k tokens
Knowledge cutoff—30 Jun 2024
List price in / out per 1M$1.75 / $14$0.018 / $0.09
Blended price per 1M (3:1)$4.81$0.04
Cheapest hostAzure · $1.75 / $14Darkbloom · $0.018 / $0.09
Hosts on OpenRouter210
Last tested27 Oct 202626 Oct 2026

Compare any two models →

GPT-5.3-Codex vs gpt-oss-20b: frequently asked questions

Is GPT-5.3-Codex better than gpt-oss-20b?
GPT-5.3-Codex is more accurate: it answered 66 of 80 questions correctly (82.5%) against 41 of 80 (51.2%) for gpt-oss-20b. GPT-5.3-Codex is more accurate; gpt-oss-20b is cheaper.
Which is cheaper, GPT-5.3-Codex or gpt-oss-20b?
gpt-oss-20b is cheaper: $0.000066 per question as billed, against $0.01. List prices: GPT-5.3-Codex $1.75 in / $14 out, gpt-oss-20b $0.018 in / $0.09 out per million tokens.
Which is faster, GPT-5.3-Codex or gpt-oss-20b?
Their output speed is similar: 95 and 103 tokens per second.
Which has the larger context window, GPT-5.3-Codex or gpt-oss-20b?
GPT-5.3-Codex, with 400k tokens against 131k.