The other thing to think about is how things will change in the future. We did our will when dd (our eldest) was a baby. 4 possible future guardians:-
Sibling 1 - married, two kids in primary school
Sibling 2 - single, no kids
Sibling 3 - married, no kids
Friends - local, married, unable to have kids but desperate for a baby, saw dd a lot
From this it seems like a toss up between sibling 1 and friends.
Fast forward a few years and we now have two kids and the situation is very different:-
Sibling 1 - youngest child now in college, lives abroad a lot of the year
Sibling 2 - married with a child (we are named guardians)
Sibling 3 - married with a child
Friends - large family of their own through adoption.
Siblings 2 and 3 now looking far more appropriate.
What we did was name both sets of parents as guardians (in laws as main and my parents as back up) and state that we wanted the two families to work together to decide on the best people to have residence. We have also discussed with parents every now and then who we thought it should be - which has changed over the years.