I used the Diamond dampener on a 3302 for 15+ years. I'm surprised to hear it is still available. I considered it fantastic but eventually replaced it for the 5 roller Altra Crestline. I'm going to guess that Crestlines outsold Diamonds in my region 20 to 1. On the occasions when I wanted help neither the service techs I had available nor any operator anywhere were familiar with them.
Look at the cost of replacing the rollers. I cannot recall if there were 2 or 3 (rubber) rollers subject to wear. I do recall I would occasionally skip replacing one of them. The form is significantly larger than other dampening forms and I'm thinking it's cost usually made me choke; hence, skipping the replacement of other rolls.
Both systems can do great work, but I would advise you look at the cost of full roller replacement which is necessary on a periodic basis. The dealer offering the units should be able to quote roller cost.