In theory, a longer cable will have higher resistance.
This will influence the damping factor of your amplifier, which will, again in theory influence the ability of your amplifier to have control over your loudspeakers, wihich would be a little diffirent for both loudspeakers.
I think the question can it be heard all depends on the system, the listener and the length the cables differ.
You state you want to extrct every last bit out of your set-up, than I wouldn't use different lengths:)
This will influence the damping factor of your amplifier, which will, again in theory influence the ability of your amplifier to have control over your loudspeakers, wihich would be a little diffirent for both loudspeakers.
I think the question can it be heard all depends on the system, the listener and the length the cables differ.
You state you want to extrct every last bit out of your set-up, than I wouldn't use different lengths:)