I have both.
Plus for Noppoo: POM keycaps more durable. No shininess after being used daily for over a year and half. The ABS keys on my Keycool are already starting to get shiny after a couple months. I assume that the PBT keycaps on the white Noppoos will wear similarly.
Plus for Keycool: Better layout, with Home/End keys usable without having to press the Fn key. Having Pause/Print where it is on the Noppoo is completely idiotic.
Plus for Keycool: I like the higher-profile keycaps.
Plus for Noppoo: wider right Ctrl key. I use this key a lot and it's nice to have the extra size.
Minus for Keycool: The pad printing on the keycaps is very thick.
Minus for Keycool: I've had some problems where a key will register as stuck down if I press it only down just to the activation point.
My perfect keyboard would have the Keycool Home/End layout, Noppoo modifier layout, and POM keycaps.
Here's a pic I took of both on the day I got my Keycool, after using the Noppoo daily for 18 months. As you can see, no wear/shininess on the Noppoo keys at all.