Definitely Kuching. Way more atmosphere (KK was flattened in WWII, while Kuching still has the colonial buildings). I liked Bako National Park...fascinating microclimates and some of the oldest-growth forest in the world.

The lower Kinabatangan is really fascinating, BTW. I took an Uncle Tan tour there for a night. That operation is very basic, but cost maybe a fourth what the others wanted at the time. A highlight is the flashlight nighttime boat tours, where you can see snakes dangling from trees and the like (Guides are very good at spotting stuff). We also saw 2 orangutans high up in the trees. It'll be memorable.