To the "the brain is still developing, we need to make the age 25" group:  why stop at pot legalization?  Make it the same with alcohol.  And while we're at it how about other decisions that should require a fully mature brain: military service - disregarding that the rashness of youth is why the age is 18 because by 25 it is far less likely they would voluntarily sign up.  And then on to contracts, especially those student loans.  
Or we could recognize that almost all the propaganda about pot has been from the US and it's full intention was to discredit Hispanic people, Black people and anti war protesters and was never at any time based on health.  Pot has been available to me my whole life, 50+ years, however I've never used it.  I agree that education needs to be ramped up to inform on possible long term health impacts but then I also believe that should be done for a variety of other legal drugs: alcohol, caffeine, OTC drugs (ex. Tylenol - kills more than pot yearly).