It may just be the location where it is set.
We install them every day, and frankly, there are subtle differences when installed.
Looking at the porcelain pieces, they seem identical.
What does change, is the plumbing in the homes.
I know from a plumbing standpoint, that there are many ways to run the pipes depending on the framing.
I don't always equate noise with quality of flush though.
The first Ultramax I ever installed is very quiet. And yet it doesn't seem to plug. That was about ten years ago.
I kind of think they made them nosier just to make people "feel" like it was working harder. Most of the flush is below the surface, the water rushes from the siphon jet, and out the back.
Go ahead, drop a quarter in the bowl and then flush.