Here I concur with you, the darker the tobacco, the richer it’s taste. While I enjoy some toasts and love Madras for nicotine, my “desert island snuff” would be neftobak - moist, coarse and dark. And yes, it does have a mysterious, very special note, like no other snuff - probably inherited from wooden casks where it’s been maturated. It’s made from air cured burley.
Sometimes I get out of this world fruityness and schmalzer-like aromas from huge pinches of NTSU. On a clean nose, that is, with no other snuffs taken before.