Originally Posted by Darth Moeller
Thats what I thought. When Luke asks if the Dark side is stronger, Yoda tells him no.
Yoda isn't exactly impartial though, obviously he would think than the Side he's the foremost practitioner of is the "best". And he would likely tell Luke what he needed to hear to make Luke do as he wanted.
It could also depend on how you measure the "power" of the sides, and what use you intend for it. If you need to wreak destruction and violence then the Dark side is clearly stronger. But the Force isn't merely a weapon, there are other aspects to it, which are less useful in situations or fighting and struggle, in which the Light side might be stronger. As has been mentioned before, the Dark side might be more powerful, but the power "burns out" the user quicker than the Light side would.