Moai SDK vs Codea

Because it uses Lua + C++.

You can use your own custom shaders and extend the language with C++. MOAI doesn't give you everything, instead it gives you the tools you need to develop any game you want.

So it is extendable with C++

Uses a limited subset of Lua

Moai SDK is used by popular developers including Double Fine for their mobile game, Middle Manager of Justice, and for their Kickstarter hit, Broken Age(formerly, Double Fine Adventure.) It was also used to create the popular mobile game Bubble Ball 2.
This proves that this engine can be used to make fully-featured and fun games.

Has options for development like Hanappe and Rapanui, providing a different way to interact with the engine.

The Moai SDK Forum is active and users will go to great extents to answer queries, post code snippets, beta test, and even purchase and give feedback on each others' games.

Although the Moai SDK is very advanced and uses complicated features, the documentation wiki thoroughly and clearly explains how to use these features, such as the Moai Cloud(a service that provides web services for your game), and multiple ways to build from source.

Errors show up live, as you type. Smarter autocompletion picks up your local and global variables, including nested types. Everything else is just plain smarter, from indentation to highlighting.

Codea ships with three great music and sound packs, composed just for Codea and free for you to use in whatever you create.

Location library lets you make use of the GPS inside your iPad. Get your latitude, longitude, altitude and more with a dead-simple API designed specifically for Codea.