GPT-5.6 Luna vs Grok 4.20

GPT-5.6 Luna against Grok 4.20
GPT-5.6 LunaGrok 4.20
Coding index58.033.3
Benchmarks behind it Verified, 6 benchmarks Partial, 2 benchmarks
Output $/Mtok$1.20$2.50
Cost per solved task$0.04$0.72
Context window1.05M2M