Yikes. Tough comparison because they’re two completely different experiences.
Uniqueness? Man... I think they both deliver that in spades.
Gameplay? If you were to strip away the rules and go solely on how the shots feel, I think it might be a draw. They both have a ton of good feeling shots.
Rules? DI. No question. Tons to do, lots of nostalgia, clever risks and rewards. Mate that with a brilliant layout, and it only gets better for the game.
Sound/music: WH2O wins, without pause. Sure, the quality is better on DI, but it was my biggest personal disappointment with the game. I really wanted to hear some tasty Chris Granner licks and tunes on the game. Instead, we got an understated soundtrack that feels really lackluster to me. The compounding raft tunes of white water has unmatched depth and breadth for a Pinball soundtrack, even by today’s standards.
DI is a Pat Lawlor masterpiece, imho. It’ll keep your interest longer, it’s got a ton to do, it’s got really good flow, tons of toys and technology, comparing it to WH2O is like comparing an EM to a solid state game.
I know I’ll never give up my WH2O, but I’d probably sell every other game in my collection to finance a DI. I’ve thought about it more than once.