Most things, in my estimation. A lot of that is just preference on my part, but having watched the boyfriend play a good chunk of The Witcher 3 side-by-side with my gaming on Inquisition, I never felt the urge to switch games.
Story-wise, I find The Witcher's story convoluted and hard to follow. My boyfriend actually stopped and restarted for that reason. He has numerous complaints about the gameplay, as well, with XP being hard to come by and sudden jumps in the static levels of the enemy.
Visually, both have stunning graphics, but stunning graphics are almost something expected with this generation of games. I like what DAI chose to turn that perfect camera towards. The Witcher suffers from serious "real is brown" that plagued DA's first two games. The medieval vilages look authentic, and authentically ugly. I've never seen such well-rendered pigpens. The cutscenes are nicely rendered, but there's a lot of them. Like JRPG a lot. It looks like a movie sometimes.
But for me, the clincher is Geralt himself. I don't like him. He's a thirteen-year-old boy's power fantasy. With boys-only clubhouse of powers that include perfect birth control and immunity to STIs - he's a mutant for consequence-free sex! - and that breathy voice that bad action-movie voice that sounds like he's having breathing problems. There's even a section in the strat guide about all the women he can have sex with!
It feels one giant leap below DAI's relationships in terms of maturity.
I also find it odd that a community that once wanted Origins 2 for the next DA game now wants them to model their next game after the most static protagoist in the current RPG gen.
Add to that so much fantasy boilerplate with no deconstruction, right down to typical dwarves with Scottish accents, and there's not much to recommend it. It feels like it belongs to another era.
The sidequests look well-done. And engaging, and better-written than the main plot. That's all I can find to recommend it, and the only thing I might want the devs to look at.