Whirlpool DDs
I think what made the DDs so famous was two things:
1. The bulk of Whirlpool machines were sold under the Kenmore name. Sears knew how to sell, and they turned everything into gold under their name. Kenmore gave low price, high end features on low end models (ie today you can get sani-rinse on a BOL Kenmore, but outside of that you must go to at upper MOL), large capacity, warranty, service contracts, ect ect. Bottom line their was all the incentive in the world for people to buy Kenmore, and Whirlpool had all the incentive to build a machine that gave the most bang for the buck.
2. The GE and Maytag change over was a disaster:
a. GE has always leaned toward builders and landlords, and in the 90s the Welch magic kicked in possessing everything with greed and an even bigger desire to appeal to the buider's grade market. A market GE won over in the 70s and 80s. As such the post FF washers were never really intended to be stellar or durable machines, rather appealing to a market that was never really intended for joe consumer.
b. Maytag always had joe consumer in mind, but made a lot of mistakes. In an effort to compete with Whirlpool they copy-pasted several designs without actually improving them or simply coming up with their own. The end result was horrible reliability that destroyed their reputation.
Personally DDs do shred, but only on the fast setting which is why Kenmore made sure low-fast was their "normal" cycle.