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  5. GPT-6 LunavsOpenAI o4-mini
Updated Sep 2026

GPT-6 LunavsOpenAI o4-mini

GPT-6 Luna is cheaper than OpenAI o4-mini at $0.1/M vs $1.1/M input tokens.

GPT-6 Luna and OpenAI o4-mini compared across 20 shared prompts
SpecGPT-6 LunaOpenAI o4-mini
Input price$0.1/M tokens$1.1/M tokens
Output price$0.5/M tokens$4.4/M tokens
Context window1.1M tokens—
WeightsClosedClosed
Free API (OpenRouter)NoNo
ReleasedSep 2026Apr 2025
Side by side

Same prompt, both answers

Opening lines from 2 of the 20 prompts both answered. Formatting stripped, words untouched.

Advanced Investment Memo (IC Memo)

You are writing an internal investment committee memo for a long/short equity fund. Company (fictional): LedgerLift (ticker: LLLT) – B2B…

GPT-6 Luna896 words
LedgerLift (LLLT) — Investment Committee Memo Recommendation: Short 12-month price target: $28–$42 At $46, LedgerLift’s price implies continued strong growth and margin expansion; our DCF scenarios value the shares at approximately $17–$42, with the base case near $28.
Read the full answer
OpenAI o4-mini642 words
Recommendation Short LLLT; 12-month price target $30–40 (vs. $46 today). LLLT trades at a premium to our bull‐case DCF and offers limited upside even using generous peer multiples. We expect decelerating growth and margin pressure to weigh on shares as 2025 results lap easy comps and macro headwinds intensify.
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Mini LBO Underwrite

You are underwriting a 5-year LBO for a private equity investment committee. Company (fictional): HarborTech Services (HTS) –…

GPT-6 Luna405 words
All figures in $m. Assumptions: annual Term Loan amortization is 1% of original principal ($4.8m); cash interest is based on beginning-of-year balances; Mezz PIK compounds annually.
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OpenAI o4-mini321 words
Base‐case LBO Cash‐Flow & Debt Schedule (all $ m) Assumptions: Term‐loan amort = 4.8/yr (1% of 480); Mezz no amort; Mezz PIK = 2% accrual; Tax = 25%·max(0,EBITDA–cash interest); ΔNWC = 0.5%·ΔRev; Capex = 3%·Rev; all excess cash pays Term optional.
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Our Verdict
GPT-6 Luna
GPT-6 Luna
OpenAI o4-mini
OpenAI o4-miniRunner-up

Not enough votes to call it. On the specs, GPT-6 Luna has the edge: bigger model tier, newer, bigger context window.

GPT-6 Luna costs 8.8x less per token.

Too close to call

Reviewing agent-written code?See a Brief PR report

API pricing

Cost per 1M tokens

GPT-6 Luna
Input
$0.10
11× cheaper
Output
$0.50
8.8× cheaper
OpenAI o4-mini
Input
$1.10
Output
$4.40

GPT-6 Luna is cheaper on both: 11× input, 8.8× output.

Where to run it

4 hosts, cheapest first

GPT-6 Luna3 hosts
HostInOutContextUptime
Azure AI Foundry$0.10 in·$0.50 out·1.1M·88.4% upOpenAI$0.10 in·$0.50 out·1.1M·99.9% upAmazon Bedrock$0.11 in·$0.55 out·1.1M·99.8% up
OpenAI o4-mini1 host
HostInOutContextUptime
OpenAI$1.10 in·$4.40 out·200k·100% up

Per million tokens. Prices and uptime via OpenRouter, checked 25 Sep 2026.

Research

What we learned reading every model

FAQ

Common questions

Both are developed by OpenAI but target different use cases. You can compare their actual outputs across 20 challenges on Rival to see how they differ in practice.

It depends on your use case. GPT-6 Luna and OpenAI o4-mini each have strengths in different areas. Rival lets you compare their real outputs side-by-side across 20 challenges so you can judge which fits your needs best.

GPT-6 Luna costs $0.1/M input tokens and OpenAI o4-mini costs $1.1/M input tokens. GPT-6 Luna is $1.00/M cheaper per input. Check their side-by-side outputs on Rival to see if the price difference is justified by quality.

This page shows a side-by-side comparison of GPT-6 Luna and OpenAI o4-mini across shared challenges. You can vote on which model produced the better output in a blind duel. Browsing and voting are free. No account is needed to look; signing in only saves your votes and likes.

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Model pages

GPT-6 Luna logo
GPT-6 Luna20 outputs, specs and price
OpenAI o4-mini logo
OpenAI o4-mini59 outputs, specs and price
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