ym2616 has the famous “ladder effect” glitch where the negative edge of waveforms get nudged out of place creating a unique distortion effect. Even other ym chips like the 3438 don’t have it, so like they say in their videos the 2612 has the potential to be dirtier than the dn.
Also in CH3 mode the MEGAfm won’t have fixed ratios, and I think the DN has only fixed ratios. (edit: recent firmware update added ratio offsets)
Different applications of aliasing will also result in different sounds in the DN and the ym.