Study after study, dataset after dataset, have shown marijuana to be a less dangerous drug than alcohol. It is also a less socially destructive drug. We've also seen that better access to drugs leads to a lowering in overall drug use.

If my kids were to come to me and ask about alcohol vs marijuana, regardless of legality, I would tell them that they should aim to have small amounts of alcohol frequently and small amounts of marijuana very occasionally. If that put them in a situation whereby most of their life was sober, they still had a few drinks at an occasional party and occasionally had a joint or two, I think they'd be in good shape and still get to enjoy some great experiences that pure abstinence would withhold from them.

It's not a good idea to use either drug heavily and frequently, particularly when one's brain is still developing. With that being said, almost everyone I know has drank frequently and often pretty heavily since their teens and I haven't witnessed any of them really suffering for it.

I have, on the other hand, watched many people abuse pot from a young age and now, over a decade later, their life and mental health is a wreck. But perhaps they abused pot because they weren't mentally stable anyway and it just made things worse, but that this was somewhat inevitable?

It's hard to tell, but neither drug used in moderation will do much damage and so, legal or not, it really just remains a case of "all in moderation".