To me, it is a no contest. Shadow is eons ahead of white water.
White water is great for beginners and as a location machine. I play it when I get the chance, but I would never buy it. The game feels claustrophobic and becomes redundant too quickly for a home machine. "You are boring me!"
The Shadow is a strange one. It isn’t popular because you need to play it many times to learn its strange geometry, mechanics and rules. You have to be a good player or you’ll hate it. Once you get it, the game opens up and becomes one of the best ever made. It also poses unique solutions to problems. For example, my machine hates allowing post transfers, so I often use the switchable ramps to pass the ball. I also have to use a good deal of nudging, and my tilts are sensitive.
"You still think you can control the game with brute force?"