Fencing Gap Thoughts?

[NatJ]

I have an option between a 3 inch and 4 inch gap between the fence pickets. (4 inch more money)

Which size would you go with to keep Cochin or Buff from escaping?

Chicks will go through either gap.

Adults of those breeds will probably not go through either one. (Some adult bantams will fit through a 3 inch gap, and more will fit through a 4 inch gap.)

If chicks go through, and adults do not, there will come a point when chicks have grown too big to fit through a 3 inch gap but can still go through a 4 inch gap.