Witcher 3 is the better game in my opinion. It doesn't run as smoothly as Phantom Pain, but the open world is just so much better (in fact, I'd say it has the best open world of any game, period) and the mission variety is also a lot better. Phantom Pain's an excellent game, but the Witcher 3 has it beat hands down in terms of story, characters, mission variety and just generally being a better open world experience.