* smaller runtime foot print.
* faster runtime.
* simpler to embed
* the fewer batteries that are included are simpler to embed in your runtime. Python's libraries are often very tricky to embed.
I prefer python to lua, although they are both expressive and powerful languages, however the convenience of python isn't enough to trump the flexibility and speed of lua.
(edit formatting)
Whenever I hear someone complain about (lack of) Unicode support, my ears prick up. See, Unicode support is a many-headed beast, and almost no languages have very much of it, and most of what people naively think of as Unicode support (length, indexing into "characters", case conversion) doesn't really work when you take into account combining diacritics, ligatures, Turkish I, German S, etc.
I'm not especially familiar with Lua, but it transparently stores and compares UTF-8 strings, and there are even bindings for ICU. So what's missing from "Unicode support"? Script specifiers in regular expressions, perhaps? I'm asking out of genuine curiosity.
But no, it's fucking not OK. Lacking basic unicode handling means everyone handles unicode strings in different ways, so various libraries clutter in basic string capabilities. Sometimes this really piss me off.
Proper unicode support would include things like normalizing strings (Unicode has 4 different normal forms!) and testing for fuzzy equivalence. But last time I checked, the usual library for doing those things, libicu, was bigger than the whole Lua interpreter. So I can see why there isn't a lot of enthusiasm, especially if there isn't a real use case.
Thanks for this good news! The last time I tried Lua it didn't work. UTF-8 is ok, full Unicode is not necessary.