Actually...It's called active balancing, not dynamic...or it used to be anyway.
Given it's only done to one wheel should speak louder than anything else. A proper dynamic balance will bring both wheels into harmonious balance to eliminate the chance for what can be understood as the bicycle pedal effect (wheels fighting each other, wobbling) probably more important to how your H-D feels than even a factor change, IMHO
All they really do is change the balance factor to something a tad higher, which may or may not be noticeable.
I liken most of their positive testimonials to a psychological factor not unlike those from people who equate louder with faster, a change to a different oil with cooler running and better shifting etc. or any other number of adjustments different than what is specified as somehow being better.
They will however help on something like a wheel or clutch housing (if it's out of balance to begin with)where the component is to run in total balance, but when it comes to a flywheel assembly with a reciprocating component (pistons, top of rods) they will do nothing, or next to it!