Embedded scripting languages

What scripting language would you embed to a program? The performance would not be main issue, since the compiled part of the program would worry about that.

The scripting language would call many functions written in C, C++, or whatever lang that can compile C-like functions (so there needs to be some kind of easy to use FFI).

I thought about options here:
- Lua
- Scheme (tinyscheme or whatever)
- Something else?

Now, what would /prog/ use, and why? ("Read SICP" is not a valid answer here)

Is there any reason to use regular Lua instead of LuaJIT? They have the same C API, don't they?

The discussion here indicates that the Lua from lua.org is very slow. However, many people claim it's pretty fast and light. Faster than Python, for example. So who is right?