I am being a nitpicker here, but I think there is no correlation between country size and level of economic development. Many of the richest polities in the world are quite small. Places like Singapore & HK come to mind.
I think bigger countries, even if they are "1st world," can sometimes look rather rough, because there is a lot of variation between different regions / municipalities / neighborhoods. It can be surreal sometimes, but it is what it is.