The WItcher's decisions felt like they held a lot more weight. Especially compared to the ones you make in Mass Effect. I have not played Dragon Age, but I assume that the choices that you make are along the same lines as the Mass Effect choices. The Witcher's game even branches depending on which choice you made. That never happened in Mass Effect.
BTW, I did enjoy Mass Effect, but I think that the Witcher did choices a lot better.