I love my Innuos Zen Mk3! I remember when the Mk3 versions of both the Zen and the Zenith came out, and I was trying to decide between them. I watched a review by John Darko, in which he said that there was only a very slight difference in sound between the two (favoring the Zenith just a little) and that it still took him 2-3 days to be sure he even heard a difference. My dealer convinced me that the Zen was a better value because it had the best sound-to-cost ratio in the Innuos line.
The other thing that Innuos has going for it is its music-player software, Sense 3.0. A lot of folks who have used both Roon and Sense think that Sense has better sound quality and stability in actual use. Roon has more features (and Roon Radio is very good), but Roon is designed to work with many different types of hardware and can't be tailored to squeeze the best performance out of a dedicated hardware line like Innuos does.