Though they both have addictive properties, sex and smoking are rarely called on for a comparison round of bad qualities. Smoking would, in most instances, trump sex in the battle of the bads, unless you’re referring to certain experiences.
However, if this formula works out right: smoking can cause oral cancer and so can oral sex.
Oral sex can also lead to HPV which leads to oral cancer, but you can’t catch HPV from cigarettes. Ladies and gentlemen, we have a winner! Curious? Refer to the this lovely graphic below: