Videos can be misleading, they may give you an idea but they can't exactly tell you completely of how loud or quiet they actually are. The only real way to tell is not only hear one in person but also have a decibel meter next to it. For example this one was definitely quieter on camera.
Regarding split systems, generally they are louder because most of them are dual motor units even my next door neighbor's Silent Partner is very loud. Unless if they have the same motor as the one piece units, they are the same. There was one before that was actually one of the more quieter units I've ever used and that would be the VacuMaid S2600. I wouldn't have minded owning one if VacuMaid was still using the same colors and logo as this one hence that's one of the reasons why VacuMaid is my all time favorite central vacuum brand. But from a consumer point of view, they are not only more expensive but also I've noticed from experience they clog up the screens more than the one piece units unless if you have a bagged canister that goes with the motor.