We chose 1. Thing is, by the time they're old enough to realise the local common and woodlands isn't actually a forest, they're old enough to travel more easily if they do want to go to the country. My experience of growing up in 2 was not having friends in walking distance and having to rely on grumpy parents cars to see most friends. My kids can walk to a few friends already and will soon be old enough to get buses around to the others.
Thing with countryside is often the fields etc are private and kids can't play in them anyway (and farmers who let children play in haystacks etc years ago don't now). So need to check carefully. Speeding traffic is more of an issue outside London, ditto lack of pavements. And friends outside envy the number of school trips my kids get (the school is particularly good at seizing opps but free travel means they can easily go somewhere at short notice).
Though I grant you London is horribly crowded and expensive so very happy for people not to move here...