as a user, marijuana is definitely good. ive never smoked cigarettes, so I can't say how "good" they are. i just know they don't get me high.
I'm addicted to seltzer waters.
AFAIK the withdrawal symptoms aren't unbearable, nothing like stimulants or opiates or benzos. I'm sure that getting high sounds a lot more attractive than sitting through the withdrawal for 36 hours or however long it lasts, and that the withdrawal would impair the user infinitely more than the cannabis.
[1] https://en.m.wikipedia.org/wiki/Psilocybin#/media/File:Drug_...