For me, it tends to really depend on the pokémon. As an example, I certainly prefer Gyarados' sprite in Gold than I do in Silver, whilst I prefer Ho-oh's sprite in Silver compared to the one in Gold (the pose for me is the problem, I get tired of seeing Ho-oh's wings flapped up and its head ducked down everywhere.)
But for the majority, I prefer Silver's sprites. They appear more vibrant to me than that of Gold.