I'd have to choose alcohol if I had a choice, mostly because even though most alcohol tastes like bleach, if you're smart about it, it can actually improve your health. Smoking (that is, smoking anything) is just completely and totally silly. Intentional asphyxia for the lose.
Drinking in moderation is okay, and not going to kill you. Getting stupid drunk is never a good idea, and smoking is just disgusting no matter how you look at it. So I say: drinking, but do it smartly.
I've never smoked or drank (personal choice), but I voted smoking in the poll because atleast you can only usually kill yourself or maybe one other person with it. Drinking has the potential to kill multiple people.