Hi @wig , a lot of people seem to love the Miflex's and I'm sure they are great performers in many systems. In mine, they sounded good, but removed almost all the front to back layering that my system is capable of. I really enjoyed the Sach's pre and was feeling content with it, but when I installed the Mundorf Supremes, all of a sudden I had another 2-3 feet of meaningful depth to the imaging. I didn't know what I was missing, but in comparison, the Miflexs were almost two-dimensional.
Moving up to Mundorf Silver/Gold/Oils added another foot to the depth of the imaging (and also reduced the bass to a level that I couldn't accept until I added in new subwoofer amplifiers that could boost my bass a bit).
Moving on to the Duelund's probably took out that extra foot, but made the sound more real/natural. They're also a little cleaner and more precise in terms of locating instruments in the soundstage.
I think whether the Deulunds are worth it or not (vs the Miflexs) will really depend on the depth capabilities of your system's imaging.
It's been too long for me to accurately comment, but I want to guess that they're more tonally similar than different (whereas V-Cap TFTFs and Mundorfs will definitely both shift the tone in different directions).
Hope that helps.