I cannot compare them side by side as far as I know lua very little, but I can try to list some prominent features of haskell.
1. Haskell compiles libraries to machine codes and can be loaded as simple as dlopen() lets it.
2. Strong static typing won't let occasionally replace a handler by another one of a wrong type.
3. Even more, strong static typing allows reasoning about impossibility of non-deterministic side effects, i.e. code purity in functions that return pure types. It means, for example, that you cannot make any file operations, opening/closing/waiting sockets etc. in functions that return Int or String: comiler won't let you do that. If you want produce such side effects, then you have to wrap the returned type in IO monad.
4. Pure functions allow very aggressive code optimizations.
5. Objects immutabilty allows very simple and fast garbage collection model (there is no need to watch for global references as soon as they do not simply exist).
6. The language is quickly evolving, the latest ghc 8.0.1 released 3 or 4 months ago had lots of new impressive features. Haskell community is known to be large and friendly.
7. Declarative nature of haskell and functions as first class citizens makes programming in it a real fun and pleasure.
Anyway, I did not try to compete with the lua module, but rather I wanted to educate myself in doing haskell/C cooperation.
