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  5. GPT-6 Luna ProvsOpenAI o4-mini
Updated Sep 2026

GPT-6 Luna ProvsOpenAI o4-mini

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

GPT-6 Luna Pro and OpenAI o4-mini compared across 20 shared prompts
SpecGPT-6 Luna ProOpenAI 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 Luna Pro888 words
LedgerLift (LLLT) — Investment Committee Memo Recommendation: Pass 12-month price target range: $28–44 per share LedgerLift has attractive customer economics, recurring revenue, and a credible path to margin expansion, but those strengths are already reflected in a $46 share price.
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.
Read the full answer

Mini LBO Underwrite

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

GPT-6 Luna Pro434 words
Operating and debt schedule Conventions: Interest is calculated on beginning-of-year debt; the 1% Term Loan amortization is 1% of its original $480m principal ($4.8m annually). Mezzanine PIK accrues at 2% annually.
Read the full answer
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.
Read the full answer
Our Verdict
GPT-6 Luna Pro
GPT-6 Luna Pro
OpenAI o4-mini
OpenAI o4-miniRunner-up

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

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

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

Where to run it

3 hosts

GPT-6 Luna Pro2 hosts
HostInOutContextUptime
Azure AI Foundry$0.10 in·$0.50 out·1.1M·98.6% upOpenAI$0.10 in·$0.50 out·1.1M·99.9% 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 Pro 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 Pro costs $0.1/M input tokens and OpenAI o4-mini costs $1.1/M input tokens. GPT-6 Luna Pro 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 Pro 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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