I've lomg been a big KL fan (lots of LAX-AMS trips in WBC) but, since you have to change planes someplace, I'd go with NW. WBC on the 330 is much more comfortable, more modern, more private and more luxurious. And domestic first beats the pants off KL's intra-European "Europe Select" product, which is just a normal 3-abreast coach section with 2" more legroom, a fussier inflight meal and a free newspaper.
That said, there are a few newly-refitted KL 747s in the wild, and you might luck out and get one--but I doubt it.