Agreed Adler Eric it did have a different role to the DUKW so yes, it is unfair to compare them. The Kubel and Schwimmer's 2 wheeled drive put them at a huge disadvantage to the JEEP straight off.
Millitary vehicles have to be 4 or more wheeled drive for practical reasons the Kubel is more of a fancied up Beetle the Jeep is vastly superiour for the job.