Actually no...In the long run, Dark side always get it's crappy, corrupted and wrinkled ass kicked by storytellers. Of course occasionally sith'll have the edge simply because kicking LS's shining shaved holy butt helps them from falling madness.
If not, storytellers would become crazy as Crimson King. I mean, who could kick ugly DS ass all the time and keep his/her sanity? Kicking LS's ass gives them some luxury, like holiday after long months of work.
On other hand, what am I talking about...