The only NK bars I know of are laminated bars.
I don't like them for day-in, day-out use, as I feel they don't hold up as long. I have a Jonsered 2149 that came with one, and the bearings in the nose crapped out within about 20 hrs of use (that can be the symptom of dirt, inadequate lube, or just bad luck, but they aren't repairable) I got two Husqvarna-branded replacements on Ebay for about $10, and I bent one right away. I've also seen a few laminated bars come apart...sometimes the spot welds let go.
Regular old solid bars aren't that much more expensive, and hold up far better. I doubt if the difference in power requirements is very much between the two...I didn't notice any diff in cutting speed on the Jonsered.