As seen in many of my posts from last summer, I often drive the trails along with a friend who has a CJ-2A that has 600 x16 NDT (square shoulders). I have the NDCC because I could not find the NDT tires in the 700 x 15 size, which as I stated above, is the size my Jeep came with new.
The performance of the two Jeeps seems almost identical. I posted pics on the old forum of a trip last summer where the non-directional tires proved superior to two other Jeeps with very aggressive wider tires. Different terrain calls for different tires, I would think.