Meth is generally agreed to be the most depraved, with heroin and maybe crack in 2nd
Junkies don't get too high and hear voices, or stay up for a week diving further into delusions and psychosis, ending in violence. Junkies kick and have a nasty 10 days, and afterwards, aside from some minor paws, are fine, tweakers can be fucked for a long, long time after sobriety. Heroin doesn't really mess with judgement or perception while high
Funny thing though, back in the day, at this "shooting gallery" nasty junkie den I used to go to, you mention meth, and all these homeless junkies are all "oh my god, no", and then you hear from tweakers "whoa man you're fucked up, physically addicted and all"
Mostly just opinion