I have to agree with MikePdx. I recently acquired a Wessel Werk powered brush and have been comparing it with a three decade old Kenmore Powermate on different surfaces using the same Kenmore 4.1 vacuum. Before anyone protests, I replaced the power cord exiting the back of the Wessel Werk head with a Kenmore compatible cord (the owner of the vacuum shop I frequent found something from another brand of vacuum in blue of all colors that fit the lower socket in the Kenmore wand and we innovated from there) and use this on a Kenmore wand. It works like it was designed that way other than not being gray like the rest of the assembly.
The Kenmore/Hayden head cools the motor with suction air. That motor runs in all the dirt your vacuum is sucking up and any exhaust joins the airflow up the hose. It is not vented to the outside or cooled by outside air. The W-W head has vents on top and at the rear to cool the motor and a little cooling fan on the end. It looks like it pulls air in from the rear and vents it to the top. In any event if you turn the motor off and just use it as a suction brush the arguments about exhaust air blowing dust around are moot.
I also genuinely dislike the swivel on the W-W head. In terms of overall quality, the W-W head is cheaply made in my opinion. Yes it is lighter than the Kenmore/Hayden head, but when you take them apart it is obvious the W-W head is nowhere near as stoutly made as the Kenmore head. It won't last.
Regarding the light weight, in carpet that works against you. Just today the doggie chewed up a stuffed toy, but instead of soft stuffing it was filled with plastic pellets. Thanks for the test opportunity Gunnar! I fired up the recently refurbished Kenmore 4.1 with the W-W head and vacuumed vigorously for ten minutes or so until I could no longer hear the tell tale ticks of plastic pellets in the hose. Then I disconnected the W-W head and tried the Kenmore head. We found lots of pellets the W-W head missed. Same vacuum, just different heads. Glad I'm only into the W-W head for $40.