When I was a teenager I smoked weed and drank alcohol. When I was drunk I had unprotected sex, got into fights, and regularly threw up in alleyways. When I smoked weed I mainly giggled a lot and ate everything I could get my hands on. I do neither now, haven't touched weed in years and gave up alcohol 2 years ago. I know which I would prefer my teenagers to do though (although ultimately I would prefer them to do neither).
I watched a lecture by Professor Nutt (the scientist who got sacked for using science rather than politics to craft his view on drugs). He said that a society that encourages alcohol has a moral duty to offer safer alternatives. I agree.