Reply to New York or San Fran

After some advice from our Americano brothers

I turn 40 next year (yep sad isn't it) and I'm planning a week or so in New York or San Fransisco but can't decide which to visit.

I've always wanted to visit both and can't make my mind up - I'm going with the wife so it's not gonna be a lads party trip, more a typical tourist trip - so which should I do and why?