I have never used the Ultimate but I have two Der Wunder towels. Here are my thought from another post on the subject...
"On the Sonus Der Wunder Towel....Unfortunately the Hacker Attack resulted in the loss of my detailed (at least I thought it was detailed) review of this towel and I don?t have copy of it. I was very disappointed in the performance of this towel. The cliff note version of the review is this:
Good looking towel and the silk border is a very nice touch that other towels should consider. Also a great size. The towel is very "hard" compared to other WW microfiber towels I have used (Groits and JT International). Even after 6 washes. The towels seem to absorb water well, but become saturated enough very quickly that they don?t do a thorough finishing job and must be followed by another towel. I have experienced problems with "trails" on all my washes except for one, which was done with a much higher surface temperature to the car. I have a difficult time completely drying my 996 with both Der Wunder towels but I can completely dry the car with either the Groits or the JT International WW. I also question the durability as the stitching is already unraveling on the nice silk border after 6 washes.
Conclusion: Not a must have towel as there are better performing and more plush towels out there for less money. Should not be your only towel for drying (unless you buy a lot of them). Not a good finishing towel unless the majority of the water has already been removed from the surface. In my arsenal, the towels have been regulated to the most expensive door/hood/trunk jam towels probably in existence on Autopia."
Since that post (late August 04) I have washed the towels probably a dozen more times (even used micro restore). Still a very hard towel. Not plush. The silk continues to unravel. I have since bought some of the purple WW from Detailers Paradise to go with my aging Groits and JT International WW. Great towel. Very plush and soft. Does not leave trails and absorbs better than the Sonus towel. Just my $.02