I have had the pleasure to use both.  Based on the interface I heard today, the new Pink Faun ProISL for MSB, the Pink Faun is my pick.  Their fiber interface is superior and definitely co-developed.  What do I hear? 
- Much more decay
- Much more presence
- More micro detail retrievable
- Like a thin veil has been removed
My home DAC is the MSB Cascade.  My home server is a single Ultra.  The Dual Ultra doesn’t even make it a debate.  The dual is the best by a nice margin.  I would love a dual, but I don’t have the rack space.  
At a recent trade show, Peter from Magico heard the single Ultra.  Came in the next day and the only change was a swap for the single to the dual.  Peter was blown away and couldn’t believe that was the only change.
Magico now has a dual ultra in their showroom at the factory now.  I loaned mine to Alon to try and he bought one.