None of it is marketing. All the information I provide is through my experiences and tests.
The whole reason why I did so much research on Swift springs in general is because they're springs even with the exact same spring rates as the Hipercoil the Springs felt softer. Even on a spring dyno they both tested the same rates. The feel to them though were completely different. In fact I can run a stiffer Swift springs and it would feel softer than a hiperco's.
That is why I came to the conclusion that the Swift springs reaction rate was the cause of this.
Now the reason why this is better. The spring reacts immediately to the uneven surfaces on the ground, so the contact patch on the tire is always grounded, while the same spring rate hiperco would skip around because of the mechanical lag between the shock and the spring. This can not only be felt through the chassis, but the tire temps on the swift with the same spring rate is consistently cooler, the hiperco's tire would skip around through uneven surfaces creating heat. And ultimately because the tire is more grounded their is constant traction through a road course. All this will ultimately result in quicker laptimes. And that is the case with the experiences I have had with them.
Well bottom line- same spring rate feelable difference.
And by softer please do not misunderstand me with more roll. hmmmmm... It is more like there is high speed bump control set into the spring. It is more comfortable and smooth (which is very different from what a lot of my customers are used to)