Maybe you should call it cleaner. It is certainly more accurate because if the preamp does change the signal, by definition that is degradation.The problem (as has been discussed a lot elsewhere) is that a passive control is highly susceptible to cable issues while an active system is far less so. In addition, the control often acts to reduce the efficacy of the output coupling capacitor of the source (if it has one). This can result in reduction of bass impact as you turn the control down.
An active system can be completely immune to the effects of the interconnect cable, allowing the result to be more neutral.
That depends a lot on the construction of the line stage of course. Being aware of this fact, we designed our balanced line stages to be quite impervious to the interconnect cable(s) they drive; for this reason we often advise the customer that an expensive cable is not always needed.
Audition is important!