Ooomph, tough choice. They're both amazing.

-Shadow is super unique with its constant battle-flow, player controllable ramp divertors, sweet magnet trick, and "Arkanoid" upper playfield. Music and sound is great. Only thing to bitch about is the translite art & theme. Lots of "Crap movie/Great game" pins out there, though..Shadow, Drac, Congo, Tron

-Whitewater is just one of the best games ever. No game has sweet ramps like that. Every shot is just FUN. It's light-hearted and silly. The music seems to be polarizing, but it's one of my favorite 90's pinball soundtracks...it builds and changes as you advance which adds to the fun and excitement.

They're both just excellent and unique designs unlike any other pins out there, IMO. Can't go wrong with either...so - sorry, this probably didn't help you at all lol