I have short cable runs due to monoblocks, but never heard any difference between the two on my bass cabinets. Unfortunately never tried the 12ga on my head units.
I eventually switched to tempo electric solid core silver wiring and found it superior in all regards. I think the Duelund has wonderful tonality, but loses a bit of precision due to the stranded wire design. My old preamp had 16ga Duelund in it and I modified one input to use only a single strand of the duelund wire. Comparing to a standard input you could hear the blurring caused by the multiple strands. In the end I preferred single strand solid core silver (VH Audio) in that position as well.
I eventually switched to tempo electric solid core silver wiring and found it superior in all regards. I think the Duelund has wonderful tonality, but loses a bit of precision due to the stranded wire design. My old preamp had 16ga Duelund in it and I modified one input to use only a single strand of the duelund wire. Comparing to a standard input you could hear the blurring caused by the multiple strands. In the end I preferred single strand solid core silver (VH Audio) in that position as well.