For me, if it is about 'fitness', and not just outer, but 'inner fitness'. 'Cardio' and 'yoga' both work effectively on phsyical fitness in different ways. 'Cario' speeds you up, gets things going, pumps the blood and the energy of 'action'. I prefer the 'slowing down' process of yoga. There is no rush or speed in yoga, each move is mindfully made and the effect on physical fitness is profound (if slower and less 'dramatic'). This slowing down in yoga allows for a state of calm to develop in which, for example, meditation and healing can take place!