Duane Ludwig all day. look at his success through TJ Dillashaw. he's just a wizard when it comes to striking. Duke is good no doubt, but his fighters here lately have just been...... eh....
I feel as if Duane takes a more technical approach in terms of his striking system. he teaches correct technique and show how to correctly punch or kick without using a whole lot of power, but rather focusing on technique specifically as that's what makes you a more successful martial artist. he also teaches you how to effectively switch between southpaw and orthodox and how to comfortably fight in both of those stances.
plus I would much rather live in Westminster which is just outside of Denver and where Ludwig's gym is located. good people, beautiful scenery (mountains and such) and I love training at elevation. Milwaukee is not a good place to live or at least IMO and that's what I've heard over the years. I mean there is crime everywhere you go anymore, but the crime in Milwaukee, WI is high.
If I'm gonna live somewhere to train in MMA and potentially start a family there, I'm gonna make sure it's a safe environment for me to live in and having trained in Colorado before, I can speak for that and say Colorado would be the better choice.
So yea all in all, I would rather have Ludwig as my head striking coach, all day.