Was renting IMDN premium when I bought my DP pro and it's DP for me all day. Barely touched IM after I brought DP home.
DP: High energy, hilarious, accessible for people who aren't god-like pinball players.
IMDN: Better flow, also high energy, but much more demanding and difficult. Also I found myself getting tired of hitting the wall at a few modes, whereas I don't feel that way with DP.
In a small collection (4 here), DP is my most-played and offers plenty of depth. Unless you're just an expert and will blow through it in a week, DP is a blast.