Dragon Age: Inquisition will be released on November 18, 2014, in North America, and November 21, 2014 in EU.
The Witcher 3: Wild Hunt will be released on March 24, 2015, four months after Dragon Age: Inquisition.
We will see a lot of denials, but the two games are direct competitions. Both are the third installments in the series. Both belong to the same genre, i.e., medieval fantasy open-world sword-and-sorcery RPG with a strong focus on storytelling and characters. Both have very similar gameplay and execution, (i.e., third-person camera view, real-time tactical action combat with pause, dialogue choices that impact stories and characters, cinematic dialogues and dynamic cuts, etc.) Both will be released in the same time frame within a few months. Both are in the same generation so they are comparable in terms of technology and graphics.
Most importantly, both games will require intensive time investment. Supposedly either one will consume over a hundred hours to complete. Most adults will have the time to dedicate to only one of the two - unless someone has no job, no school, no family, and no life; then he can certainly sit in his parents' basement and play video games all days. Otherwise, adults will have to prioritize and choose, and one has to come before the other That is why the two games are competitions.
Let say you can choose one and only one. Which would you choose? Explain your choice.
Even if you say you will buy both, you must prefer one over the other. So choose.