The brush bar on the 40 has two small wheels and rollers whereas the the 41 has only rollers. The front roller tangles up with hair and fibers resulting in a less that easy operation. The rollers are easy to pop out and clean but wouldn't it be better not to have to do this in the first place. The wheels and back rollers on the 40 did not catch any hairs or fibers the two months I had it.You can see in the pic that one side of the front roller is jammed up on the 40, the 41 relies on only rollers and the back wheels to get around. Maybe the wheels and rear roller did not jam as they would be running on clean media as long as the duct was clear.
The brush bar exhaust hose and the wand hose are fixed with screws on the 41 whereas on the 40 these components clip together facilitating quick and easy
dis assembly an important factor as these two tubes are prone to blocking with household items, twigs pens tortilla chips scrunched up paper etc.
The handle on the 41 is a bit flexible, small point but easy to solve.
Shame the two teams didn't have that beer and put their heads together.
Off track but I see that the 50 brush head is completely different than the 40 or 41 with its internal motor, clever boffins at work.
Probably a complete replacement unit!
The sole plate was a right fiddle to fit correctly on the 40 I have only tried it once on the 41 and it went together first attempt. Luck maybe.
Details but out of the two machines the 41 is a clear winner in my eyes.