I'd prefer my children and I to have an understanding, where they would know they could come to me without any doubt. My parents were very hard on me, I couldn't approach them about anything. What made it worse was that I had the hard rules set on me where my (younger) brother could go do stuff I wasn't allowed to do. My parents would even buy him alcohol, but if I even had one drink, I'd be grounded. My dad would even breathalyze me.
I wouldn't encourage drinking, but I'd like to think that I'd be reasonable enough and I would rather my teen having an agreed limit if 1-2 drinks, over them getting completely blitzed. I'd rather they can talk to me about it all, rather than them being scared of what I would say or do that they hide it all from me. I'd also prefer to know where they will be, and with who, and would appreciate having a responsible adult nearby to keep an eye on things.
But hey, theres about 12 years to go before I cross this bridge, a lot of time to think and reflect, and I'm sure when we get there we will do what is right for our daughters judging by their personalities, their friends, maturity etc. There are so many variables, that I really cant give a set answer right now.