Hi Steven,
You're right, the difference in agitation between the Lindhaus and WW powerheads is noticeable. I always felt that the Lindhaus cleaned well despite its lack of aggressiveness, due to the serrations in the baseplate that allow air to flow through the carpet fibers. Lindhaus products are so often sold into commercial applications, that I believe they are designing more for commercial carpet. On deep plush, the extra agitation does help to get the sand out of the bottom of the carpet.
The system in my parents' house is a Vacuflo 760, basic hoses in garage and basement, Stealth kit downstairs, SEBO ET-2 kit upstairs. They have lots of medium plush carpet and some hard floors. There's never dirt in their carpets though, so it's not a good place to test vacuums. I really should bring the powerheads to my place (where the third floor is all deep plush carpet) and see how they fare. Right now up there I'm using a Hayden hose and powerhead...I don't mind the heavy wire-reinforced hose as much because there's only one inlet in the center and it's all open space. I can still hear cat litter getting vacuumed out of the depths of the carpet from the previous owner's cats. Guess the litter box must have been up there.