Wirtz had offers from both clubs but chose the Reds when leaving Bayer Leverkusen this past summer.
Speaking to Kicker, the Germany attacker said: "I've always had the feeling I could do what I wanted. That's why I didn't put pressure on myself to make a decision quickly. I had already thought long and hard about both clubs, and in the end, the decision wasn't easy. But I made it with absolute conviction, and I'm happy about it.
"The discussions with Arne (Slot) were very, very positive from the start. He convinced me right from the first meeting. He gave me clear ideas and a precise vision of how he could and wanted to use me in his team. This, combined with the group structure, really convinced me.
"He saw me in the number 10 role, the position in which I perform best. I was bought to play there because they had faith in me to improve the team. And I try to live up to that faith as best as possible."