I actually don't think either side is overall stronger than the other. The light uses their powers pretty much defensivley while the dark side uses pretty much offensive based powers. Now while G.L. has said that the Light Side is stronger and must defeat the darkside to bring balance, where is the balance in that? You cannot have balance when there is not two equally opposing forces, if you dont believe me pull out an old style scale and see where the balance is when one side has weight and the other has nothing.
The Light will always prevail, dark siders we have to come to that realization. Yes being all tough guy and force choking peope is cool and all but we will lose. However, we will return and make the light work to get rid of us. That is the true balance.