Except the fact that Fiddle is a module from the standard library of ruby and that ruby-ffi is an external module, what are the main differences between them.
More specificaly, what could be the reasons that lead you to use one over the other? (except the fact that one create a dependancy to an external gem).
Basically ruby-ffi is dead and not maintained any more, so just go with Fiddle.
Update: Seems that ruby-ffi is still alive, so it can be used as well as the Fiddle module.