They are two different technology used in a 3D system. In an active 3D technology, the video frames displayed to each eye are off-set against each other and fancy technology is used in active 3D glasses, while in passive 3D no technology is applied in glasses except that each lens of the passive 3D glasses is polarized by two different filters. It is hard to say who wins all credits, but passive 3D glasses obviously are cheaper on price and smaller in size than active 3D glasses while the later one can offer you a high quality.