Alcohol is far more dangerous
Compare the two long term
20 years of smoking pot every day vs 20 years of drinking everyday
20 years of pot: short term memory affected, possible stress increase(easily agitated) decreased lung function and other mild effects with the nervous system such as slowed reaction time(usually under influence, long term or not..) Chances of overdose: 0.000000000001%, you can't overdose on marijuana, the amount of THC required to cause "overdose" effect cannot be obtained in any consumption form of Pot, you will pass out before you ever get close to the level required, it is said it would require 15 pounds of pot within a 72 hour period to get to "overdose" level, which is impossible even if you smoke a joint every 2 minutes for 72 hours, it won't even be a pound..
20 years of alcohol: liver damage, colon damage, high blood pressure, brain damage, decreasing motor function, stomach damage among more effects, you can die from alcohol poisoning quite easily, 21 shots is enough to kill you, you can wreck or be hit by a drunk driver and kill you/them
You can argue pot smokers wreck too, but drunk drivers kill more people then legitimate accidents every year
Why is pot illegal? Because its too hard to tax and regulate, Marijuana has been legal twice in this country, it was legal to begin with and was a gift from Turkey's leader to the President (i don't have a clue which president) and a propaganda explosion occured over Mexican immigrants, they then put out false information stating Marijuana caused people to go insane, kill there parents, rape women etc..and that it was all coming from Mexico
After being illegal the first time they revoked it slightly after they revoked alcohol's illegal status and for much of the 1960s it was legal, it was made illegal again a few years after Woodstock, after all the bad stuff that happened there due to Acid and Sexual abuse
Fun fact: J Edgar Hoover (first director of FBI and later president) was given the task of eradicating Marijuana the first time, and while having an interview in Missiouri on a highway bridge overlooking hills of Pot he gave the statement; "They have given me an impossible task, they want me to get rid of a plant that grows everywhere"