That's a tough one, they both excel at different things. I still havent finished W3, Im gonna hold off until I get my new monitor.
I found DA:I to be Bioware at it's best. An epic RPG with a great story, lots of fun choices regarding classes and skills, party banter, pretty fun combat and the whole Keep and War Table angle were great additions to the franchise that were executed well.
Witcher 3 is a different beast. Despite it's RPG it's really lacking in what many people enjoy about RPGs. Party choices, the skill system is fairly meh overall and combat is still a weak point. But what they nailed this time out was making you feel like a Witcher out in the world. Where DA: I had it's weak points in the side quests, that seems to be where W3 has excelled. Witcher contracts and random quests are the strong point in the game, and not so the story imo, which is fairly boring.
Despite it's billing as open world, W3 felt feels fairly contained to me. I don't really feel like I'm exploring an open world so much as a big map. I actually prefer DA: I and it's "Hub Based" open world for the sake of variety. Every map felt different and that's something W3 has been lacking. Towns and villages kind of feel the same. You got your quest board, blacksmith, alchemist and someone who needs a Witchers help. The world is big and open but I don't feel like there's a lot of variety in it.
Writing this out, I realize that I prefer DA: I by a wide margin. W3 is still a great game, but DA: I was a phenomenal Bioware type of RPG which is what I've always loved. W3 has moments of greatness, like The Bloody Baron quest line which is still the high point of the game for me. Oh, yeah, and Gwent, heh. But overall I do think it's getting a bit overrated.
I strongly disagree. W3 is best when you arent playing the story and you're going around picking up random shit to do. From what I've seen, nobody really gives a shit about Ciri.