Black Denim, (Including Spice and Dark Tan) is a Denim cloth material (Cotton and polyester) that is 18oz and the OEM style (Pre 2001). Its super light and sometimes considered the cheap/budget material.
Black/Spice Sailcloth is sailcloth, a 28oz fabric that is heavier and better quality material for the soft top. This started with the 2001 model according to quadratec, but cant verify that is true.
Black Twill is 30oz fabric and is the best option/latest development.
Also, heres the link to quadratecs descriptions of each soft top material.
https://www.quadratec.com/c/howto/what-is-the-best-material-for-a-Jeep-soft-top
IMO, just pickup the Black Twill and call it a day. Buy once, Cry once. I did not do that and I still kick myself in the butt with how noisy and flappy my top is.