The only pro I can think of is you get a standard scheme set of batteries, which isn't even really a pro in this space. The biggest con is implementation size and complexity. IIRC the JITter alone is twice the size of LuaJIT's entire codebase, and not for being vastly better.

License problems too, if you're not making copyleft software. Guile is GPL, both Luas are MIT.