Considering they are different games with a different focus, its a bit of an odd comparison, like comparing Uncharted 2 and the last of us. Having said that in areas thst the two are comparsble Witcher 3 by a mile. Be it combat, story, world, humor (or lack there of in Skyrim). But Skyrim does exploration better than The Witcher 3.
Please excuse my (probally) poor grammar