Servicing and Longevity
Well, one could argue that the DD machines have been around for a bit as well. Speed Queens are not a common household brand, at least not around here. The commercial places here use Maytag, GE and SOME Huebsch (SQ). Your local, smaller repair shop probably has more experience with WP based machines based on shear numbers, they're a very common machine. I think it's in fact very safe to say that you can get more common than SQ, WP and it's derivatives outnumber SQ's quite a bit in the home as do GE's and many others.
I'm not arguing the superiority of WP to SQ, which is what I feel like this is becoming. I'm simply stating that for someone who needs a washer, who doesn't know the mechanics and just wants something that works for a reasonable prince, the WP comes out on top. SQ sells a high brow washer and charges accordingly for it. For this you get very well made machine yes, but an expensive one. That said, if I was fiscally able to do so I would certainly have a SQ set as I do like them. If I had a limited amount to spend on laundry equipment however, I'd get a basic WP variant set.
Also to the shred statements, I've always heard the DA agitator referred to as "Cruel Action" or a "Shredmore" but I've never had this issue personally. I prefer the longer stroke, but have never had issues with the WP agitator cleaing or being unusually rough on clothes. I don't wash a lot of delicates or frailies though so I can't speak there.
-Tim