I was just going to post this in the other thread about sex at 18.
I think that if they are going to make it 21 the legal age to drink, then everything should be 21 including enlisting in the army etc. Otherwise lower it back down to 18.
I have always said if they are mature enough to fight for their country, then so be it, if they want to have a beer, then let 'em.
Although I do believe it has its pros for being 21 and cons for being 18 and vice versa.