LuaJIT performance on PC is very fast when its using the JIT. However, on consoles and some mobile platforms JITing is not allowed due to not being allowed to write to executable memory for security reasons.

Mun compiles to machine code with LLVM so it should be very fast as well, hotloading overhead can be completely removed in builds where hotloading is not required (production builds for instance). Mun should therefor be able to run as fast as native code on all platforms.

Since Mun targets LLVM could it also be output to WASM to be using in-browser for HTML5 builds?

In theory yes, but we have to look into that some more. At this point we only target Windows, MacOS and Linux but WASM is definitely on our list.

LuaJIT is not available on every platform. Love2D for example is pretty slow on iOS, especially at computing paths etc for custom draw calls.

Defold is slightly different, still allowing Lua scripting, but not more than that, which is the appropriate place for Lua in a mobile-dominated market.

CoronaSDK uses Lua for IOS, Android, Windows and Mac. Our experience is its performance is sufficient for lots of games