Alright. Well, I've been a smoker, so I guess I'll post. Marijuana, in fact, has more tar, no filter, blah, blah, blah. The key difference, however, is that people that smoke weed probably aren't smoking twenty times a day. People who smoke cigarettes, and start to smoke habitually, will probably smoke a pack or more a day. Smoking cigarettes is physically more harmful to you.
However, nicotine does not store in your fat cells, and does not hinder the neurons of the brain from firing through the build up of fatty tissue. Nicotine does not alter your perceptions of the world around you, and the most a smoker will get is a body high for a few minutes after a cigarette. This is an affect which also abates after several months of smoking.
I will also say that weed smells a whole lot worse than cigarette smoke, and cigarette smoke doesn't smell good at all. Weed, even un burned, smells like someone's bad BO.
That being said, though, weed makes you an idiot, and a heavy, compulsive cigarette smoker will die before 70. They're both bad for you, so just don't do either.