The basic idea of insulation is to save money and improve the ambience of a home.
With this in mind keeping the insulation on the inside as close to the heat source as possible saves money on heating year on year and the cost of materials. The rooms warm up more quickly.
Placing the insulation on the outside of a wall, means you are heating the wall as well as the comfort zone of your home, and warming takes longer and costs more year after year.
If you are retired and are at home with the heating on all the time then exterior insulation in or out doesn't matter.
If you go out a lot and turn the heating off or down frequently internal insulation saves money and gives increased comfort.