Marijuana does not affect a person's body nearly as much as alcohol and is not as harmful to people as alcohol. Despite it being illegal many people prefer Marijuana over alcohol and so they should. The long term use of alcohol compared to marijuana has greater risks, and anyone that has ever used both drugs would know that the effects of alcohol on the body are much greater than marijuana, which would mean than in the long run alcohol would be harder on the body.
Marijuana is in the form of a plant and is usually smoked in the form of a cigarette, or sometimes in a pipe, bong, vaporizer, or other types of smoking paraphernalia, or less commonly it can be ingested. Alcohol is in the form a liquid and is always drank, often mixed with another beverage to make it taste better. Compared to each other alcohol would be better in the sense that alcohol is only drank and marijuana is smoked and is not necessarily good for your lungs, compared to cigarettes marijuana is not as bad, but smoking anything is not "good" for a person. Alcohol may not be as bad to put in your body as marijuana but once it is in there it is a lot worse.
Marijuana affects mostly the brain, a lot of people smoke it to get "high" or "stoned" but the high of marijuana is nothing compared to harder drugs like cocaine or heroine, it is more like a mellowed out feeling that can make a person feel somewhat lazy. Most people who smoke it say that it makes them more creative and some say it opens there mind up and they are smarter, and at the same time the person is still in reality where the high from other drugs can take a person right out of reality. Alcohol when it is taken gets into the bloodstream and usually only takes a few drinks to give a person a "buzz". Now if a person only takes a few drinking they are usually fine, but if they take a few more they will usually get drunk and most people say they get drunk to have a good time but when a person is drunk they may act completely different, their coordination is off and they become impaired.