I live near three liquor stores. I'm not sure of the difference, other than one sells the product that gets you wasted, and the other sells a potential delivery system.
FWIW, I also live near two head shops and an endless sea of tacky motels. Ahh good ol Colfax Avenue......but get about a block away from it, at least in most parts of Lakewood, and it's as residential and non-descript as anywhere else in the country.
Other differences are that what a liquor store sells can lead to fatal overdose or induce violent behavior, unlike what is consumed using what a head shop sells. (Also, the former is more addictive than the latter.)