A modern house so probably not a trational Ogee.
I don't like pencil round skirtings in any age of house, they look cheap.
If you are specifying, I think three inch looks too small. Builders like to put in the smallest ones to save money.
Modern skirtings are usually white MDF. It's OK looking if you are going to paint it and it will never get wet. If you want a stained finish it must be wood; preferably selected when you go to the timbermerchant to avoid the knotty ones. Stained boards look better if fixed with brass screws, not nails, and this also makes it easier to remove them undamaged when necessary.