Do a search at Vinyl Asylum for a post by Fretless regarding both Moerch arms. He has a UP-4 and has listened to the DP-6 as well.
I have used a DP-6 with 12" red wand for nearly 3 years, and have been very pleased with it. It sounds very good and it is flexible with cartridge matching. Some people will not like the feel of the UP-4 since the unipivot causes it to flop around when you handle it. That doesn't necessarily affect the sound, but it can affect how you interact with the arm which is important for long term satisfaction. The DP-6 has a very solid feel.
Dave
I have used a DP-6 with 12" red wand for nearly 3 years, and have been very pleased with it. It sounds very good and it is flexible with cartridge matching. Some people will not like the feel of the UP-4 since the unipivot causes it to flop around when you handle it. That doesn't necessarily affect the sound, but it can affect how you interact with the arm which is important for long term satisfaction. The DP-6 has a very solid feel.
Dave