Dennis Grant makes some good points in his website and I completely agree on the subject of dyno plots.
If a vendor is not willing to supply the plots either they don't have a clue what they are selling or they don't have confidence in their product. Dyno plots are a very very useful marketing tool and IMO vendors should take full advantage of it. I always skeptical of unproven dampers because of the large number of Asian knockoffs/cheap manufacturing. Even Koni yellows are iffy. Dampers are not something where 5 thousands doesn't make a difference. .005" could make a difference between a seal sealing properly and a huge amount of hysteresis and inconsistent damping.
That being said - will the average street driver notice .005"? Hell no, thats they the Koni yellows are such a good value. But the step above that are the Monotube 28/30series Koni's and the Penskes, Motons etc. I'd even be willing to put the OTS Bilsteins above the Yellows because they are monotube.