I did the overlapping when I did all my Insulation...then a friend, who was a builder all his life, told me to staple it all inside. So I redid all my insulation.
He said that it was for getting to the studs easier and if you want to tuck speaker wires for TV cable or anything else, its easier to run it next to the studs.
Personally, I think you could do it eather way...it does look nicer on the inside. and it was faster and easier to locate each stud.