Well, it's not an IDE, so it's not fair to compare it to Pharo which is trying to be both a runtime environment and an IDE. If anything, it's an advantage that Ruby allows you to make choices about the development environment you use.

I think it's fair to compare the language+environment which is the only thing that practically matters. Smalltalk has a really nice IDE and fast VM. Ruby doesn't have a native IDE, but does well with things like Vim & Notepad++. Ruby has a lot more modules and Rails. I wouldn't consider Ruby to be very fast being one of the slowest popular languages out there.