I think it's a toss-up, personally, on the way out. I'd give a slight edge to CO only because I like to sleep and KL's earlier departure is awfully taxing on the body clock.

On the way back, I'd sacrifice the non-stop for a one-stop on NW via DTW, MSP, or MEM, choosing an Airbus 330 flight. Why? Because NW has a nice selection of on-demand audio and video, which helps pass the time on the daytime flight. And free booze. Plus as a CO Gold, you have a very good chance of getting upgraded on the domestic NW segment.