The wall thickness of the pipes is different as well as the inner structure of the PVC. Many years ago, all I would use would be schedule 40 PVC pipe for house plumbing.

Armacell now offers new sizes for its flexible AP Armaflex pipe insulation. The new sizes start at 8-inch inside diameter tubes by 1-inch wall and go up to 10-inch inside diameter tubes by 2-inch wall ...