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.

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.