I agree Jamerson is more complex than Dunn, but I wouldn't say the margin is that wide. Dunn is the reason I picked up bass, followed closely by Steve Harris.
A big factor might be that Jamerson was very free to come up with his own lines after he demonstrated his ability to come up with improvised parts that often defined, if not rewrote the tunes. He was a Jazz upright guy first. Dunn OTH often (but not always) was dictated parts by Steve Cropper. Duck was a R n B electric guy first. His lines were much more diatonic in origin than JJ's. There is a large margin in the complexity, maybe because of the differing song materials they worked with. Both were masters of their craft and art.
