In terms of cancer, cigars tend to produce cancer of the digestive system — stomach, intestines, colon — more often than cigarettes, which cause more lung cancer due to more inhalation. Both cause cancers of the mouth, throat and esophagus. In those respects they are more or less equal.
The big difference is that cigarettes also partially saturate your blood with carbon monoxide, a poisonous gas. Even though it does not reach lethal levels from the cigarettes, it can displace oxygen in up to 50% of your red blood cells, which prevents your organs (including your brain) from receiving the support they need. Over time, when combined with nicotine’s property of causing blood vessels to contract, this leads to heart and other circulatory problems.
Either is a lousy choice.