Judge the shoe by how it fits on your foot. Select a shoe that conforms as nearly as possible to the shape of your foot. Have your feet measured regularly. The size of your feet changes as you grow older. Have BOTH feet measured.
Most people have one foot larger than the other.
Fit to the largest foot. Fit at the end of the day when your feet are largest. Your heel should fit comfortably in the shoe with a minimum amount of slippage. Walk in the shoe to make sure it fits and feels right.